diff --git a/.changes/unreleased/Fixed-20250128-130242.yaml b/.changes/unreleased/Fixed-20250128-130242.yaml
new file mode 100644
index 000000000..bd03e44b4
--- /dev/null
+++ b/.changes/unreleased/Fixed-20250128-130242.yaml
@@ -0,0 +1,6 @@
+kind: Fixed
+body: Add validation error to manual selection of person in PersonDuplicateController
+time: 2025-01-28T13:02:42.369442185+01:00
+custom:
+    Issue: "350"
+    SchemaChange: No schema change
diff --git a/src/Bundle/ChillPersonBundle/Controller/PersonDuplicateController.php b/src/Bundle/ChillPersonBundle/Controller/PersonDuplicateController.php
index b11390a46..348a3495d 100644
--- a/src/Bundle/ChillPersonBundle/Controller/PersonDuplicateController.php
+++ b/src/Bundle/ChillPersonBundle/Controller/PersonDuplicateController.php
@@ -29,6 +29,7 @@ use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
 use Symfony\Component\Security\Core\Security;
+use Symfony\Contracts\Translation\TranslatorInterface;
 use function count;
 
 class PersonDuplicateController extends \Symfony\Bundle\FrameworkBundle\Controller\AbstractController
@@ -40,6 +41,7 @@ class PersonDuplicateController extends \Symfony\Bundle\FrameworkBundle\Controll
         private readonly EventDispatcherInterface $eventDispatcher,
         private readonly Security $security,
         private readonly \Doctrine\Persistence\ManagerRegistry $managerRegistry,
+        private readonly TranslatorInterface $translator,
     ) {}
 
     #[\Symfony\Component\Routing\Annotation\Route(path: '/{_locale}/person/{person1_id}/duplicate/{person2_id}/confirm', name: 'chill_person_duplicate_confirm')]
@@ -125,7 +127,14 @@ class PersonDuplicateController extends \Symfony\Bundle\FrameworkBundle\Controll
             $person2 = $form->get('person')->getData();
 
             if (null === $person2) {
-                throw $this->createNotFoundException("Person with id {$person2->getId}() not".' found on this server');
+                throw $this->createNotFoundException('Person not found on this server');
+            }
+
+            // Validation: Ensure person1 is not the same as person2
+            if ($person->getId() === $person2->getId()) {
+                $this->addFlash('error', $this->translator->trans('Person1 cannot be the same as Person2'));
+
+                return $this->redirectToRoute('chill_person_duplicate_view', ['person_id' => $person2->getId()]);
             }
 
             $direction = $form->get('direction')->getData();
diff --git a/src/Bundle/ChillPersonBundle/translations/messages.fr.yml b/src/Bundle/ChillPersonBundle/translations/messages.fr.yml
index 6b3c5cd0e..dd4c9c3ba 100644
--- a/src/Bundle/ChillPersonBundle/translations/messages.fr.yml
+++ b/src/Bundle/ChillPersonBundle/translations/messages.fr.yml
@@ -127,6 +127,7 @@ not-duplicate: Faux-positif
 Switch to truefalse: Marquer comme faux-positif
 Switch to duplicate: Marquer comme doublon
 No duplicate candidates: Il n'y a pas de doublons détectés, ni de faux-positifs
+Person1 cannot be the same as Person2: La personne que vous sélectionnez ne peut pas être la même que celle de ce dossier.
 
 # addresses part
 address_street_address_1: Adresse ligne 1