diff --git a/src/Collection/Set.php b/src/Collection/Set.php
index e2d14d0..6c2d736 100644
--- a/src/Collection/Set.php
+++ b/src/Collection/Set.php
@@ -88,6 +88,23 @@ public function add($element): self
         return self::fromPointer($elements);
     }
 
+    /**
+     * @param Set<T> $elements
+     *
+     * @return Set<T>
+     */
+    public function addAll(Set $elements): self
+    {
+        $new = $this->elements;
+        foreach ($elements->elements as $current) {
+            if (!$this->contains($current)) {
+                $new[] = $current;
+            }
+        }
+
+        return self::fromPointer($new);
+    }
+
     /**
      * @param T $element
      *
diff --git a/tests/Collection/SetTest.php b/tests/Collection/SetTest.php
index 0dd5290..e12ab31 100644
--- a/tests/Collection/SetTest.php
+++ b/tests/Collection/SetTest.php
@@ -275,4 +275,12 @@ public function testSetDisjoint()
         self::assertFalse(Set::of('a', 'b', 'c')->disjoint(Set::of('d', 'b', 'f')));
         self::assertFalse(Set::of('a', 'b', 'c')->disjoint(Set::of('d', 'e', 'c')));
     }
+
+    public function testSetAddAll()
+    {
+        self::assertTrue(Set::of('a', 'b', 'c')->equals(Set::of('a')->addAll(Set::of('b', 'c'))));
+        self::assertTrue(Set::of('a', 'b', 'c')->equals(Set::empty()->addAll(Set::of('a', 'b', 'c'))));
+        self::assertTrue(Set::empty()->equals(Set::empty()->addAll(Set::empty())));
+        self::assertTrue(Set::of('a', 'b', 'c')->equals(Set::of('a')->addAll(Set::of('a', 'b', 'c'))));
+    }
 }