diff --git a/api/src/identity-access-management/infrastructure/repositories/user-to-create.repository.js b/api/src/identity-access-management/infrastructure/repositories/user-to-create.repository.js
index 61ceede393..56395b3459 100644
--- a/api/src/identity-access-management/infrastructure/repositories/user-to-create.repository.js
+++ b/api/src/identity-access-management/infrastructure/repositories/user-to-create.repository.js
@@ -1,7 +1,10 @@
 import { PGSQL_UNIQUE_CONSTRAINT_VIOLATION_ERROR } from '../../../../db/pgsql-errors.js';
 import { DomainTransaction } from '../../../../lib/infrastructure/DomainTransaction.js';
 import { STUDENT_RECONCILIATION_ERRORS } from '../../../shared/domain/constants.js';
-import { OrganizationLearnerAlreadyLinkedToUserError } from '../../../shared/domain/errors.js';
+import {
+  AlreadyRegisteredEmailError,
+  OrganizationLearnerAlreadyLinkedToUserError,
+} from '../../../shared/domain/errors.js';
 import { User } from '../../domain/models/User.js';
 
 /**
@@ -55,8 +58,14 @@ async function _createWithUsername({ knexConnection, user }) {
  * @private
  */
 async function _createWithoutUsername({ knexConnection, user }) {
-  const result = await knexConnection('users').insert(user).returning('*');
-  return _toUserDomain(result[0]);
+  try {
+    const result = await knexConnection('users').insert(user).returning('*');
+    return _toUserDomain(result[0]);
+  } catch (error) {
+    if (error.constraint === 'users_email_unique' && error.code === PGSQL_UNIQUE_CONSTRAINT_VIOLATION_ERROR) {
+      throw new AlreadyRegisteredEmailError();
+    }
+  }
 }
 
 /**
diff --git a/api/tests/identity-access-management/integration/infrastructure/repositories/user-to-create.repository.test.js b/api/tests/identity-access-management/integration/infrastructure/repositories/user-to-create.repository.test.js
index e484a5d0d2..f5c6371986 100644
--- a/api/tests/identity-access-management/integration/infrastructure/repositories/user-to-create.repository.test.js
+++ b/api/tests/identity-access-management/integration/infrastructure/repositories/user-to-create.repository.test.js
@@ -1,7 +1,10 @@
 import { User } from '../../../../../src/identity-access-management/domain/models/User.js';
 import { UserToCreate } from '../../../../../src/identity-access-management/domain/models/UserToCreate.js';
 import { userToCreateRepository } from '../../../../../src/identity-access-management/infrastructure/repositories/user-to-create.repository.js';
-import { OrganizationLearnerAlreadyLinkedToUserError } from '../../../../../src/shared/domain/errors.js';
+import {
+  AlreadyRegisteredEmailError,
+  OrganizationLearnerAlreadyLinkedToUserError,
+} from '../../../../../src/shared/domain/errors.js';
 import { catchErr, databaseBuilder, expect, knex } from '../../../../test-helper.js';
 
 describe('Integration | Identity Access Management | Infrastructure | Repository | user-to-create', function () {
@@ -80,6 +83,30 @@ describe('Integration | Identity Access Management | Infrastructure | Repository
         expect(userSaved.cgu).to.equal(user.cgu);
         expect(userSaved.locale).to.equal(user.locale);
       });
+
+      context('when email is already taken', function () {
+        it('throws an AlreadyRegisteredEmailError', async function () {
+          // given
+          const alreadyExistingEmail = 'already_used_for_another_account@example.net';
+          databaseBuilder.factory.buildUser({ id: 7, email: alreadyExistingEmail });
+          await databaseBuilder.commit();
+
+          const now = new Date('2022-02-01');
+          const user = new UserToCreate({
+            firstName: 'laura',
+            lastName: 'lune',
+            email: alreadyExistingEmail,
+            createdAt: now,
+            updatedAt: now,
+          });
+
+          // when
+          const error = await catchErr(userToCreateRepository.create)({ user });
+
+          // then
+          expect(error).to.be.instanceOf(AlreadyRegisteredEmailError);
+        });
+      });
     });
   });
 });