diff --git a/app/controllers/france_connect/particulier_controller.rb b/app/controllers/france_connect/particulier_controller.rb
index 3eb3c494d..6f9cbda83 100644
--- a/app/controllers/france_connect/particulier_controller.rb
+++ b/app/controllers/france_connect/particulier_controller.rb
@@ -58,6 +58,12 @@ class FranceConnect::ParticulierController < ApplicationController
 
     destination_path = destination_path(user)
     render :confirmation_sent, locals: { email:, destination_path: }
+  rescue ActiveRecord::RecordInvalid => e
+    if e.record.errors.where(:email, :taken)
+      redirect_to new_user_session_path, alert: t('errors.messages.france_connect.email_taken', reset_link: new_user_password_path)
+    else
+      redirect_to new_user_session_path, alert: t('errors.messages.france_connect.unknown_error')
+    end
   end
 
   def merge
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 4725ab107..c7341c757 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -751,6 +751,9 @@ en:
       # # etablissement_fail: 'Désolé, nous n’avons pas réussi à enregistrer l’établissement correspondant à ce numéro SIRET'
       france_connect:
         connexion: "Error trying to connect to France Connect."
+        forbidden_html: "Only citizen can use FranceConnect. As an instructor or administrator, you should <a href='%{reset_link}'>reset your password</a>."
+        email_taken: "This email is already in use. You should <a href='%{reset_link}'>reset your password</a>."
+        unknown_error: "An error occured, please retry."
       evil_regexp: The regular expression you have entered is potentially dangerous and could lead to performance issues.
       mismatch_regexp: The provided example must match the regular expression
       syntax_error_regexp: The syntax of the regular expression is invalid
diff --git a/config/locales/fr.yml b/config/locales/fr.yml
index 93e40c552..8fb2c88b2 100644
--- a/config/locales/fr.yml
+++ b/config/locales/fr.yml
@@ -757,6 +757,8 @@ fr:
       france_connect:
         connexion: "Erreur lors de la connexion à France Connect."
         forbidden_html: "Seul-e-s les usagers peuvent se connecter via France Connect. En tant qu’instructeur ou administrateur, nous vous invitons à <a href='%{reset_link}'>réininitialiser votre mot de passe</a>."
+        email_taken: "Cet email est déjà utilisé. Nous vous invitons à <a href='%{reset_link}'>réininitialiser votre mot de passe</a>."
+        unknown_error: "Une erreure est survenue. Veuillez réessayer."
       evil_regexp: L'expression régulière que vous avez entrée est potentiellement dangereuse et pourrait entraîner des problèmes de performance
       mismatch_regexp: L'exemple doit correspondre à l'expression régulière fournie
       syntax_error_regexp: La syntaxe de l'expression régulière n'est pas valide
diff --git a/spec/controllers/france_connect/particulier_controller_spec.rb b/spec/controllers/france_connect/particulier_controller_spec.rb
index 6fe560588..5eb8c0165 100644
--- a/spec/controllers/france_connect/particulier_controller_spec.rb
+++ b/spec/controllers/france_connect/particulier_controller_spec.rb
@@ -253,6 +253,27 @@ describe FranceConnect::ParticulierController, type: :controller do
         subject
       end
     end
+
+    context 'when associating the user conflict with existing one' do
+      let(:fci) { instance_double('FranceConnectInformation') }
+      let(:email) { 'user@example.com' }
+      let(:user) { instance_double('User', id: 1) }
+      let(:destination_path) { '/' }
+
+      before do
+        create(:user, email:)
+        invalid_user = build(:user, email:)
+        allow(FranceConnectInformation).to receive(:find_by).with(merge_token: merge_token).and_return(fci)
+        allow(fci).to receive(:valid_for_merge?).and_return(true)
+        allow(fci).to receive(:email_france_connect).and_return(email)
+        invalid_user.valid?
+        allow(fci).to receive(:associate_user!).and_raise(ActiveRecord::RecordInvalid.new(invalid_user))
+      end
+
+      it 'fails' do
+        subject
+      end
+    end
   end
 
   describe '#confirm_email' do