diff --git a/back/src/users/resolvers/mutations/__tests__/editProfile.integration.ts b/back/src/users/resolvers/mutations/__tests__/editProfile.integration.ts
index 3e7eeaa78a..d6e1bf0373 100644
--- a/back/src/users/resolvers/mutations/__tests__/editProfile.integration.ts
+++ b/back/src/users/resolvers/mutations/__tests__/editProfile.integration.ts
@@ -26,6 +26,43 @@ export const UPDATE_TRACKING_CONSENT = gql`
 `;
 
 describe("mutation editProfile", () => {
+  it("should not allow name with less than 2 letters", async () => {
+    const user = await userFactory();
+    const { mutate } = makeClient({ ...user, auth: AuthType.Session });
+    const newName = "A";
+    const { errors } = await mutate(EDIT_PROFILE, {
+      variables: { name: newName }
+    });
+    const updatedUser = await prisma.user.findUniqueOrThrow({
+      where: { id: user.id }
+    });
+    expect(errors).toEqual([
+      expect.objectContaining({
+        message: `Le nom doit contenir au moins 2 lettres.`,
+        extensions: expect.objectContaining({ code: ErrorCode.BAD_USER_INPUT })
+      })
+    ]);
+    expect(updatedUser.name).toEqual(user.name);
+  });
+
+  it("should not allow name with only special characters", async () => {
+    const user = await userFactory();
+    const { mutate } = makeClient({ ...user, auth: AuthType.Session });
+    const newName = ".-";
+    const { errors } = await mutate(EDIT_PROFILE, {
+      variables: { name: newName }
+    });
+    const updatedUser = await prisma.user.findUniqueOrThrow({
+      where: { id: user.id }
+    });
+    expect(errors).toEqual([
+      expect.objectContaining({
+        message: `Le nom doit contenir au moins 2 lettres.`,
+        extensions: expect.objectContaining({ code: ErrorCode.BAD_USER_INPUT })
+      })
+    ]);
+    expect(updatedUser.name).toEqual(user.name);
+  });
   afterAll(resetDatabase);
   it("should edit user profile", async () => {
     const user = await userFactory();
@@ -91,7 +128,7 @@ describe("mutation editProfile", () => {
     // Then
     expect(errors).toEqual([
       expect.objectContaining({
-        message: `The name cannot be an empty string`,
+        message: `Le nom doit contenir au moins 2 lettres.`,
         extensions: expect.objectContaining({
           code: ErrorCode.BAD_USER_INPUT
         })
@@ -118,7 +155,7 @@ describe("mutation editProfile", () => {
     // Then
     expect(errors).toEqual([
       expect.objectContaining({
-        message: `The name cannot be an empty string`,
+        message: `Le nom doit contenir au moins 2 lettres.`,
         extensions: expect.objectContaining({
           code: ErrorCode.BAD_USER_INPUT
         })
diff --git a/back/src/users/resolvers/mutations/__tests__/joinWithInvite.integration.ts b/back/src/users/resolvers/mutations/__tests__/joinWithInvite.integration.ts
index a41be92b42..ba7665e139 100644
--- a/back/src/users/resolvers/mutations/__tests__/joinWithInvite.integration.ts
+++ b/back/src/users/resolvers/mutations/__tests__/joinWithInvite.integration.ts
@@ -16,6 +16,53 @@ const JOIN_WITH_INVITE = `
 `;
 
 describe("joinWithInvite mutation", () => {
+  it("should not allow name with less than 2 letters", async () => {
+    const company = await companyFactory();
+    const invitee = "shortname@td.io";
+    const invitation = await prisma.userAccountHash.create({
+      data: {
+        email: invitee,
+        companySiret: company.siret!,
+        role: "MEMBER",
+        hash: "hash-shortname"
+      }
+    });
+    const { errors } = await mutate(JOIN_WITH_INVITE, {
+      variables: {
+        inviteHash: invitation.hash,
+        name: "A",
+        password: "P4a$$woRd_1234"
+      }
+    });
+    expect(errors).not.toBeUndefined();
+    expect(errors?.[0].message).toBe(
+      "Le nom doit contenir au moins 2 lettres."
+    );
+  });
+
+  it("should not allow name with only special characters", async () => {
+    const company = await companyFactory();
+    const invitee = "specialchars@td.io";
+    const invitation = await prisma.userAccountHash.create({
+      data: {
+        email: invitee,
+        companySiret: company.siret!,
+        role: "MEMBER",
+        hash: "hash-specialchars"
+      }
+    });
+    const { errors } = await mutate(JOIN_WITH_INVITE, {
+      variables: {
+        inviteHash: invitation.hash,
+        name: ".-",
+        password: "P4a$$woRd_1234"
+      }
+    });
+    expect(errors).not.toBeUndefined();
+    expect(errors?.[0].message).toBe(
+      "Le nom doit contenir au moins 2 lettres."
+    );
+  });
   let mutate: ReturnType<typeof makeClient>["mutate"];
   beforeAll(() => {
     const testClient = makeClient();
@@ -146,7 +193,9 @@ describe("joinWithInvite mutation", () => {
 
     // Then
     expect(errors).toBeDefined();
-    expect(errors[0].message).toContain("Le champ ne peut pas être vide.");
+    expect(errors[0].message).toContain(
+      "Le nom doit contenir au moins 2 lettres."
+    );
   });
 
   it("should accept other pending invitations", async () => {
diff --git a/back/src/users/resolvers/mutations/__tests__/signup.integration.ts b/back/src/users/resolvers/mutations/__tests__/signup.integration.ts
index ae8697237c..abaa9030a7 100644
--- a/back/src/users/resolvers/mutations/__tests__/signup.integration.ts
+++ b/back/src/users/resolvers/mutations/__tests__/signup.integration.ts
@@ -20,6 +20,49 @@ const SIGNUP = `
 `;
 
 describe("Mutation.signup", () => {
+  it("should not allow name with less than 2 letters", async () => {
+    const user = {
+      email: "shortname@td.io",
+      name: "A",
+      phone: "06 00 00 00 00"
+    };
+    const { errors } = await mutate<Pick<Mutation, "signup">>(SIGNUP, {
+      variables: {
+        userInfos: {
+          email: user.email,
+          password: viablePassword,
+          name: user.name,
+          phone: user.phone
+        }
+      }
+    });
+    expect(errors).not.toBeUndefined();
+    expect(errors?.[0].message).toBe(
+      "Le nom doit contenir au moins 2 lettres."
+    );
+  });
+
+  it("should not allow name with only special characters", async () => {
+    const user = {
+      email: "specialchars@td.io",
+      name: ".-",
+      phone: "06 00 00 00 00"
+    };
+    const { errors } = await mutate<Pick<Mutation, "signup">>(SIGNUP, {
+      variables: {
+        userInfos: {
+          email: user.email,
+          password: viablePassword,
+          name: user.name,
+          phone: user.phone
+        }
+      }
+    });
+    expect(errors).not.toBeUndefined();
+    expect(errors?.[0].message).toBe(
+      "Le nom doit contenir au moins 2 lettres."
+    );
+  });
   let mutate: ReturnType<typeof makeClient>["mutate"];
   beforeAll(() => {
     const testClient = makeClient();
@@ -91,7 +134,9 @@ describe("Mutation.signup", () => {
 
     // Then
     expect(errors).not.toBeUndefined();
-    expect(errors?.[0].message).toBe("Le champ ne peut pas être vide.");
+    expect(errors?.[0].message).toBe(
+      "Le nom doit contenir au moins 2 lettres."
+    );
   });
 
   it("should return the same result if email already exist", async () => {
diff --git a/back/src/users/resolvers/mutations/editProfile.ts b/back/src/users/resolvers/mutations/editProfile.ts
index d8fe4963fe..4eb75be34e 100644
--- a/back/src/users/resolvers/mutations/editProfile.ts
+++ b/back/src/users/resolvers/mutations/editProfile.ts
@@ -23,8 +23,16 @@ export async function editProfileFn(
   const editProfileSchema = yup.object({
     name: yup
       .string()
-      .test("empty", "The name cannot be an empty string", name =>
-        isDefined(name) ? !!name && name.trim().length > 0 : true
+      .test(
+        "at-least-2-letters",
+        "Le nom doit contenir au moins 2 lettres.",
+        name => {
+          if (!isDefined(name)) return true;
+          if (!name) return false;
+          const trimmed = name.trim();
+          const letterCount = (trimmed.match(/[\p{L}]/gu) || []).length;
+          return letterCount >= 2;
+        }
       )
       .isSafeSSTI(),
     phone: yup.string(),
diff --git a/back/src/users/resolvers/mutations/joinWithInvite.ts b/back/src/users/resolvers/mutations/joinWithInvite.ts
index 73d0526001..2a4d2ec4be 100644
--- a/back/src/users/resolvers/mutations/joinWithInvite.ts
+++ b/back/src/users/resolvers/mutations/joinWithInvite.ts
@@ -15,9 +15,14 @@ const validationSchema = yup.object({
     .required("Le nom est un champ requis")
     .isSafeSSTI()
     .test(
-      "not-empty-or-spaces",
-      "Le champ ne peut pas être vide.",
-      value => !!value && value.trim().length > 0
+      "at-least-2-letters",
+      "Le nom doit contenir au moins 2 lettres.",
+      value => {
+        if (!value) return false;
+        const trimmed = value.trim();
+        const letterCount = (trimmed.match(/[\p{L}]/gu) || []).length;
+        return letterCount >= 2;
+      }
     ),
   password: yup
     .string()
diff --git a/back/src/users/resolvers/mutations/signup.ts b/back/src/users/resolvers/mutations/signup.ts
index b2bfafe28a..69f9b4de92 100644
--- a/back/src/users/resolvers/mutations/signup.ts
+++ b/back/src/users/resolvers/mutations/signup.ts
@@ -17,9 +17,15 @@ function validateArgs(args: MutationSignupArgs) {
         .isSafeSSTI()
         .required("Vous devez saisir nom et prénom.")
         .test(
-          "not-empty-or-spaces",
-          "Le champ ne peut pas être vide.",
-          value => !!value && value.trim().length > 0
+          "at-least-2-letters",
+          "Le nom doit contenir au moins 2 lettres.",
+          value => {
+            if (!value) return false;
+            const trimmed = value.trim();
+            // Count letters (unicode)
+            const letterCount = (trimmed.match(/[\p{L}]/gu) || []).length;
+            return letterCount >= 2;
+          }
         ),
       email: yup
         .string()