diff --git a/openff/evaluator/datasets/curation/components/conversion.py b/openff/evaluator/datasets/curation/components/conversion.py
index a707342f..ec3be49a 100644
--- a/openff/evaluator/datasets/curation/components/conversion.py
+++ b/openff/evaluator/datasets/curation/components/conversion.py
@@ -59,7 +59,11 @@ class ConvertExcessDensityData(CurationComponent):
     def _molecular_weight(cls, smiles):
 
         from openff.toolkit.topology import Molecule
-        from openmm import unit as openmm_unit
+
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         molecule = Molecule.from_smiles(smiles, allow_undefined_stereo=True)
 
diff --git a/openff/evaluator/datasets/curation/components/filtering.py b/openff/evaluator/datasets/curation/components/filtering.py
index 4f58d160..25fe6460 100644
--- a/openff/evaluator/datasets/curation/components/filtering.py
+++ b/openff/evaluator/datasets/curation/components/filtering.py
@@ -686,7 +686,11 @@ def _apply(
     ) -> pandas.DataFrame:
 
         from openff.toolkit.topology import Molecule
-        from openmm import unit as openmm_unit
+
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         def filter_function(data_row):
 
diff --git a/openff/evaluator/datasets/taproom/taproom.py b/openff/evaluator/datasets/taproom/taproom.py
index 592408c9..8ba9cef1 100644
--- a/openff/evaluator/datasets/taproom/taproom.py
+++ b/openff/evaluator/datasets/taproom/taproom.py
@@ -189,7 +189,11 @@ def _build_substance(
             The built substance.
         """
         from openff.toolkit.topology import Molecule
-        from openmm import unit as openmm_unit
+
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         substance = Substance()
 
diff --git a/openff/evaluator/datasets/thermoml/thermoml.py b/openff/evaluator/datasets/thermoml/thermoml.py
index 80f57071..0d69ef7b 100644
--- a/openff/evaluator/datasets/thermoml/thermoml.py
+++ b/openff/evaluator/datasets/thermoml/thermoml.py
@@ -846,7 +846,11 @@ def _smiles_to_molecular_weight(smiles):
         """
 
         from openff.toolkit.topology import Molecule
-        from openmm import unit as openmm_unit
+
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         try:
 
diff --git a/openff/evaluator/forcefield/system.py b/openff/evaluator/forcefield/system.py
index a8cff76a..410098e0 100644
--- a/openff/evaluator/forcefield/system.py
+++ b/openff/evaluator/forcefield/system.py
@@ -7,7 +7,11 @@
 if TYPE_CHECKING:
 
     from openff.toolkit.topology import Topology
-    from openmm import System
+
+    try:
+        from openmm import System
+    except ImportError:
+        from simtk.openmm import System
 
 
 class ParameterizedSystem(TypedBaseModel):
@@ -31,7 +35,11 @@ def topology_path(self) -> str:
     def topology(self) -> "Topology":
 
         from openff.toolkit.topology import Molecule, Topology
-        from openmm import app
+
+        try:
+            from openmm import app
+        except ImportError:
+            from simtk.openmm import app
 
         pdb_file = app.PDBFile(self._topology_path)
 
@@ -51,7 +59,10 @@ def system_path(self) -> str:
 
     @property
     def system(self) -> "System":
-        import openmm
+        try:
+            import openmm
+        except ImportError:
+            from simtk import openmm
 
         with open(self._system_path) as file:
             system = openmm.XmlSerializer.deserialize(file.read())
diff --git a/openff/evaluator/protocols/analysis.py b/openff/evaluator/protocols/analysis.py
index 309d8a6b..1f74a6ee 100644
--- a/openff/evaluator/protocols/analysis.py
+++ b/openff/evaluator/protocols/analysis.py
@@ -34,7 +34,11 @@
 )
 
 if typing.TYPE_CHECKING:
-    import openmm
+
+    try:
+        import openmm
+    except ImportError:
+        from simtk import openmm
 
 
 E0 = 8.854187817e-12 * unit.farad / unit.meter  # Taken from QCElemental
@@ -578,8 +582,12 @@ def _extract_charges(
             The charge on each atom in the system if any are present, otherwise
             none.
         """
-        import openmm
-        from openmm import unit as openmm_unit
+        try:
+            import openmm
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk import openmm
+            from simtk.openmm import unit as openmm_unit
 
         forces = [
             system.getForce(force_index)
diff --git a/openff/evaluator/protocols/coordinates.py b/openff/evaluator/protocols/coordinates.py
index 3c0af38c..25f197e7 100644
--- a/openff/evaluator/protocols/coordinates.py
+++ b/openff/evaluator/protocols/coordinates.py
@@ -7,7 +7,11 @@
 from os import path
 
 import numpy as np
-from openmm import app
+
+try:
+    from openmm import app
+except ImportError:
+    from simtk.openmm import app
 
 from openff.evaluator import unit
 from openff.evaluator.attributes import UNDEFINED
@@ -446,7 +450,11 @@ def _execute(self, directory, available_resources):
 
         import mdtraj
         from openeye import oechem, oedocking
-        from openmm import unit as openmm_unit
+
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         if (
             len(self.ligand_substance.components) != 1
diff --git a/openff/evaluator/protocols/forcefield.py b/openff/evaluator/protocols/forcefield.py
index d5802000..5c522067 100644
--- a/openff/evaluator/protocols/forcefield.py
+++ b/openff/evaluator/protocols/forcefield.py
@@ -12,9 +12,17 @@
 from enum import Enum
 
 import numpy as np
-import openmm
+
+try:
+    import openmm
+except ImportError:
+    from simtk import openmm
 import requests
-from openmm import app
+
+try:
+    from openmm import app
+except ImportError:
+    from simtk.openmm import app
 
 from openff.evaluator.attributes import UNDEFINED
 from openff.evaluator.forcefield import (
@@ -547,7 +555,10 @@ def _built_template(molecule, force_field_source):
         openmm.app.ForceField
             The force field template.
         """
-        from openmm import unit as openmm_unit
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         initial_request_url = force_field_source.request_url
         empty_stream = io.BytesIO(b"\r\n")
@@ -643,7 +654,10 @@ def _parameterize_molecule(self, molecule, force_field_source, cutoff):
         openmm.System
             The parameterized system.
         """
-        from openmm import unit as openmm_unit
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         template = self._built_template(molecule, force_field_source)
 
@@ -682,7 +696,10 @@ def _apply_opls_mixing_rules(system):
         system: openmm.System
             The system object to apply the OPLS mixing rules to.
         """
-        from openmm import unit as openmm_unit
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         forces = [system.getForce(index) for index in range(system.getNumForces())]
         forces = [force for force in forces if isinstance(force, openmm.NonbondedForce)]
@@ -825,7 +842,10 @@ def _run_tleap(molecule, force_field_source, directory):
         str
             The file path to the `rst7` file.
         """
-        from openmm import unit as openmm_unit
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         # Change into the working directory.
         with temporarily_change_directory(directory):
diff --git a/openff/evaluator/protocols/gradients.py b/openff/evaluator/protocols/gradients.py
index c52a091f..7ccc018d 100644
--- a/openff/evaluator/protocols/gradients.py
+++ b/openff/evaluator/protocols/gradients.py
@@ -52,7 +52,10 @@ class ZeroGradients(Protocol, abc.ABC):
 
     def _execute(self, directory, available_resources):
 
-        from openmm import unit as openmm_unit
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         force_field_source = ForceFieldSource.from_json(self.force_field_path)
 
diff --git a/openff/evaluator/protocols/openmm.py b/openff/evaluator/protocols/openmm.py
index 0484b42e..4a5a6319 100644
--- a/openff/evaluator/protocols/openmm.py
+++ b/openff/evaluator/protocols/openmm.py
@@ -45,7 +45,11 @@
 
 if TYPE_CHECKING:
 
-    import openmm
+    try:
+        import openmm
+    except ImportError:
+        from simtk import openmm
+
     from mdtraj import Trajectory
     from openff.toolkit.topology import Topology
     from openff.toolkit.typing.engines.smirnoff import ForceField
@@ -84,8 +88,12 @@ def _evaluate_energies(
     -------
         The array containing the evaluated potentials.
     """
-    import openmm
-    from openmm import unit as openmm_unit
+    try:
+        import openmm
+        from openmm import unit as openmm_unit
+    except ImportError:
+        from simtk import openmm
+        from simtk.openmm import unit as openmm_unit
 
     integrator = openmm.VerletIntegrator(0.1 * openmm_unit.femtoseconds)
 
@@ -178,7 +186,10 @@ def _compute_gradients(
         The amount to perturb for the force field parameter by.
     """
 
-    import openmm
+    try:
+        import openmm
+    except ImportError:
+        from simtk import openmm
 
     gradients = defaultdict(list)
     observables.clear_gradients()
@@ -334,9 +345,14 @@ class OpenMMEnergyMinimisation(BaseEnergyMinimisation):
 
     def _execute(self, directory, available_resources):
 
-        import openmm
-        from openmm import app
-        from openmm import unit as openmm_unit
+        try:
+            import openmm
+            from openmm import app
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk import openmm
+            from simtk.openmm import app
+            from simtk.openmm import unit as openmm_unit
 
         platform = setup_platform_with_resources(available_resources)
 
@@ -445,7 +461,10 @@ def __init__(self, file, append=False):
 
         def report(self, simulation, state):
 
-            from openmm import app
+            try:
+                from openmm import app
+            except ImportError:
+                from simtk.openmm import app
 
             if self._dcd is None:
 
@@ -486,7 +505,11 @@ def __init__(self, protocol_id):
     def _execute(self, directory, available_resources):
 
         import mdtraj
-        from openmm import app
+
+        try:
+            from openmm import app
+        except ImportError:
+            from simtk.openmm import app
 
         # We handle most things in OMM units here.
         temperature = self.thermodynamic_state.temperature
@@ -596,9 +619,14 @@ def _setup_simulation_objects(self, temperature, pressure, available_resources):
             the simulation.
         """
 
-        import openmm
         import openmmtools
-        from openmm import app
+
+        try:
+            import openmm
+            from openmm import app
+        except ImportError:
+            from simtk import openmm
+            from simtk.openmm import app
 
         # Create a platform with the correct resources.
         if not self.allow_gpu_platforms:
@@ -678,7 +706,10 @@ def _write_checkpoint_file(self, current_step_number, context):
         context: openmm.Context
             The current OpenMM context.
         """
-        import openmm
+        try:
+            import openmm
+        except ImportError:
+            from simtk import openmm
 
         # Write the current state to disk
         state = context.getState(
@@ -831,7 +862,10 @@ def _resume_from_checkpoint(self, context):
         int
             The current step number.
         """
-        import openmm
+        try:
+            import openmm
+        except ImportError:
+            from simtk import openmm
 
         current_step_number = 0
 
@@ -953,7 +987,10 @@ def _simulate(self, context, integrator):
         integrator: openmm.Integrator
             The integrator to evolve the simulation with.
         """
-        from openmm import app
+        try:
+            from openmm import app
+        except ImportError:
+            from simtk.openmm import app
 
         # Define how many steps should be taken.
         total_number_of_steps = (
diff --git a/openff/evaluator/protocols/paprika/coordinates.py b/openff/evaluator/protocols/paprika/coordinates.py
index b9653475..79fcd3b9 100644
--- a/openff/evaluator/protocols/paprika/coordinates.py
+++ b/openff/evaluator/protocols/paprika/coordinates.py
@@ -141,7 +141,11 @@ class PreparePullCoordinates(_PrepareAPRCoordinates):
 
     def _execute(self, directory, available_resources):
 
-        from openmm import app
+        try:
+            from openmm import app
+        except ImportError:
+            from simtk.openmm import app
+
         from paprika.evaluator import Setup
 
         atom_indices_by_role = _atom_indices_by_role(
@@ -177,7 +181,12 @@ class PrepareReleaseCoordinates(_PrepareAPRCoordinates):
     def _execute(self, directory, available_resources):
 
         import mdtraj
-        from openmm import app
+
+        try:
+            from openmm import app
+        except ImportError:
+            from simtk.openmm import app
+
         from paprika.evaluator import Setup
 
         mdtraj_trajectory = mdtraj.load_pdb(self.complex_file_path)
@@ -248,7 +257,12 @@ class AddDummyAtoms(Protocol):
     def _execute(self, directory, available_resources):
 
         import parmed.geometry
-        from openmm import NonbondedForce, XmlSerializer, app
+
+        try:
+            from openmm import NonbondedForce, XmlSerializer, app
+        except ImportError:
+            from simtk.openmm import NonbondedForce, XmlSerializer, app
+
         from paprika.evaluator import Setup
 
         # Extract the host atoms to determine the offset of the dummy atoms.
diff --git a/openff/evaluator/protocols/paprika/restraints.py b/openff/evaluator/protocols/paprika/restraints.py
index cb33bd90..f9912555 100644
--- a/openff/evaluator/protocols/paprika/restraints.py
+++ b/openff/evaluator/protocols/paprika/restraints.py
@@ -350,7 +350,11 @@ def load_restraints(cls, file_path: str):
 
     def _execute(self, directory, available_resources):
 
-        from openmm import XmlSerializer
+        try:
+            from openmm import XmlSerializer
+        except ImportError:
+            from simtk.openmm import XmlSerializer
+
         from paprika.restraints.openmm import (
             apply_dat_restraint,
             apply_positional_restraints,
diff --git a/openff/evaluator/protocols/yank.py b/openff/evaluator/protocols/yank.py
index af0646cd..f0181bbb 100644
--- a/openff/evaluator/protocols/yank.py
+++ b/openff/evaluator/protocols/yank.py
@@ -154,7 +154,11 @@ def _get_residue_names_from_role(substances, coordinate_path, role):
         """
 
         from openff.toolkit.topology import Molecule, Topology
-        from openmm import app
+
+        try:
+            from openmm import app
+        except ImportError:
+            from simtk.openmm import app
 
         if role is None:
             return "all"
@@ -461,7 +465,10 @@ def _run_yank(directory, available_resources, setup_only) -> Dict[str, Any]:
 
             if setup_only is True:
 
-                from openmm import unit as openmm_unit
+                try:
+                    from openmm import unit as openmm_unit
+                except ImportError:
+                    from simtk.openmm import unit as openmm_unit
 
                 return {
                     "free_energy": {
@@ -1327,7 +1334,10 @@ def _analyze_phase(
 
     def _execute(self, directory, available_resources):
 
-        from openmm import XmlSerializer
+        try:
+            from openmm import XmlSerializer
+        except ImportError:
+            from simtk.openmm import XmlSerializer
 
         solute_components = [
             component
diff --git a/openff/evaluator/tests/test_protocols/test_coordinates.py b/openff/evaluator/tests/test_protocols/test_coordinates.py
index f322ee49..67700672 100644
--- a/openff/evaluator/tests/test_protocols/test_coordinates.py
+++ b/openff/evaluator/tests/test_protocols/test_coordinates.py
@@ -4,7 +4,11 @@
 import tempfile
 
 import pytest
-from openmm.app import PDBFile
+
+try:
+    from openmm.app import PDBFile
+except ImportError:
+    from simtk.openmm.app import PDBFile
 
 from openff.evaluator.backends import ComputeResources
 from openff.evaluator.protocols.coordinates import (
diff --git a/openff/evaluator/tests/test_protocols/test_openmm.py b/openff/evaluator/tests/test_protocols/test_openmm.py
index 95c82676..6e0a333b 100644
--- a/openff/evaluator/tests/test_protocols/test_openmm.py
+++ b/openff/evaluator/tests/test_protocols/test_openmm.py
@@ -10,7 +10,12 @@
 import numpy
 from openff.toolkit.topology import Molecule, Topology
 from openff.toolkit.typing.engines.smirnoff import ForceField
-from openmm import unit as openmm_unit
+
+try:
+    from openmm import unit as openmm_unit
+except ImportError:
+    from simtk.openmm import unit as openmm_unit
+
 from smirnoff_plugins.handlers.nonbonded import DoubleExponential
 
 from openff.evaluator import unit
diff --git a/openff/evaluator/tests/test_protocols/test_paprika.py b/openff/evaluator/tests/test_protocols/test_paprika.py
index 5168369c..00d044be 100644
--- a/openff/evaluator/tests/test_protocols/test_paprika.py
+++ b/openff/evaluator/tests/test_protocols/test_paprika.py
@@ -216,8 +216,13 @@ def test_prepare_pull_coordinates(tmp_path, dummy_complex, window_index, expecte
 def test_add_dummy_atoms(tmp_path, dummy_complex):
 
     import mdtraj
-    import openmm
-    from openmm import unit as openmm_unit
+
+    try:
+        import openmm
+        from openmm import unit as openmm_unit
+    except ImportError:
+        from simtk import openmm
+        from simtk.openmm import unit as openmm_unit
 
     # Create an empty system to add the dummy atoms to.
     system_path = os.path.join(tmp_path, "input.xml")
@@ -303,8 +308,10 @@ def validate_generated_restraints(restraints_path, expected_restraint_types, pha
 
 
 def validate_system_file(system_path, expected_force_groups):
-
-    import openmm
+    try:
+        import openmm
+    except ImportError:
+        from simtk import openmm
 
     assert os.path.isfile(system_path)
 
@@ -371,8 +378,10 @@ def test_generate_release_restraints(tmp_path, complex_file_path, restraints_sch
 def test_apply_attach_restraints(
     tmp_path, dummy_complex, complex_file_path, attach_restraints_path
 ):
-
-    import openmm
+    try:
+        import openmm
+    except ImportError:
+        from simtk import openmm
 
     with open(os.path.join(tmp_path, "system.xml"), "w") as file:
         file.write(openmm.XmlSerializer.serialize(openmm.System()))
@@ -396,8 +405,10 @@ def test_apply_attach_restraints(
 def test_apply_pull_restraints(
     tmp_path, dummy_complex, complex_file_path, pull_restraints_path
 ):
-
-    import openmm
+    try:
+        import openmm
+    except ImportError:
+        from simtk import openmm
 
     with open(os.path.join(tmp_path, "system.xml"), "w") as file:
         file.write(openmm.XmlSerializer.serialize(openmm.System()))
@@ -421,8 +432,10 @@ def test_apply_pull_restraints(
 def test_apply_release_restraints(
     tmp_path, dummy_complex, complex_file_path, release_restraints_path
 ):
-
-    import openmm
+    try:
+        import openmm
+    except ImportError:
+        from simtk import openmm
 
     with open(os.path.join(tmp_path, "system.xml"), "w") as file:
         file.write(openmm.XmlSerializer.serialize(openmm.System()))
diff --git a/openff/evaluator/tests/test_protocols/test_yank.py b/openff/evaluator/tests/test_protocols/test_yank.py
index 727b469b..00d8af27 100644
--- a/openff/evaluator/tests/test_protocols/test_yank.py
+++ b/openff/evaluator/tests/test_protocols/test_yank.py
@@ -214,8 +214,10 @@ def test_compute_state_energy_gradients(tmpdir):
 
 
 def test_analyze_phase(monkeypatch, tmpdir):
-
-    from openmm import unit as openmm_unit
+    try:
+        from openmm import unit as openmm_unit
+    except ImportError:
+        from simtk.openmm import unit as openmm_unit
 
     # Generate the required inputs
     build_tip3p_smirnoff_force_field().json(os.path.join(tmpdir, "ff.json"))
diff --git a/openff/evaluator/tests/test_utils/test_openmm.py b/openff/evaluator/tests/test_utils/test_openmm.py
index b33a0ca3..5852cc58 100644
--- a/openff/evaluator/tests/test_utils/test_openmm.py
+++ b/openff/evaluator/tests/test_utils/test_openmm.py
@@ -4,7 +4,12 @@
 import mdtraj
 import numpy
 import numpy as np
-import openmm
+
+try:
+    import openmm
+except ImportError:
+    from simtk import openmm
+
 import pytest
 from openff.toolkit.topology import Molecule, Topology
 from openff.toolkit.typing.engines.smirnoff import ForceField, vdWHandler
@@ -14,8 +19,13 @@
     LibraryChargeHandler,
     VirtualSiteHandler,
 )
-from openmm import unit as openmm_unit
-from openmm.app import PDBFile
+
+try:
+    from openmm import unit as openmm_unit
+    from openmm.app import PDBFile
+except ImportError:
+    from simtk.openmm import unit as openmm_unit
+    from simtk.openmm.app import PDBFile
 
 from openff.evaluator import unit
 from openff.evaluator.backends import ComputeResources
diff --git a/openff/evaluator/tests/test_workflow/test_workflow.py b/openff/evaluator/tests/test_workflow/test_workflow.py
index 80a2bb87..0ac13654 100644
--- a/openff/evaluator/tests/test_workflow/test_workflow.py
+++ b/openff/evaluator/tests/test_workflow/test_workflow.py
@@ -270,8 +270,10 @@ def test_replicated_ids():
 
 
 def test_find_relevant_gradient_keys(tmpdir):
-
-    from openmm import unit as openmm_unit
+    try:
+        from openmm import unit as openmm_unit
+    except ImportError:
+        from simtk.openmm import unit as openmm_unit
 
     force_field = ForceField()
 
diff --git a/openff/evaluator/utils/openmm.py b/openff/evaluator/utils/openmm.py
index e6da26be..88ef0534 100644
--- a/openff/evaluator/utils/openmm.py
+++ b/openff/evaluator/utils/openmm.py
@@ -6,9 +6,16 @@
 from typing import TYPE_CHECKING, List, Optional, Tuple
 
 import numpy
-import openmm
-from openmm import app
-from openmm import unit as _openmm_unit
+
+try:
+    import openmm
+    from openmm import app
+    from openmm import unit as _openmm_unit
+except ImportError:
+    from simtk import openmm
+    from simtk.openmm import app
+    from simtk.openmm import unit as _openmm_unit
+
 from pint import UndefinedUnitError
 
 from openff.evaluator import unit
@@ -40,7 +47,10 @@ def setup_platform_with_resources(compute_resources, high_precision=False):
     Platform
         The created platform
     """
-    from openmm import Platform
+    try:
+        from openmm import Platform
+    except ImportError:
+        from simtk.openmm import Platform
 
     # Setup the requested platform:
     if compute_resources.number_of_gpus > 0:
diff --git a/openff/evaluator/utils/packmol.py b/openff/evaluator/utils/packmol.py
index 6d05a0d1..6402d9c1 100644
--- a/openff/evaluator/utils/packmol.py
+++ b/openff/evaluator/utils/packmol.py
@@ -306,7 +306,10 @@ def _ion_residue_name(molecule):
     str
         The residue name of the ion
     """
-    from openmm import unit as openmm_unit
+    try:
+        from openmm import unit as openmm_unit
+    except ImportError:
+        from simtk.openmm import unit as openmm_unit
 
     element_symbol = molecule.atoms[0].element.symbol
     charge_symbol = ""
diff --git a/setup.cfg b/setup.cfg
index 4dc67272..df76a484 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -8,6 +8,10 @@ omit =
     # Omit generated versioneer
     openff/evaluator/_version.py
 
+[coverage:report]
+exclude_lines =
+    except ImportError:
+
 [flake8]
 # Flake8, PyFlakes, etc
 max-line-length = 88