Cannot set headers after they are sent : response.redirect() NodeJS

You are redirecting the user multiple times. These if are not exclusives. You should, at minima, use else if statement

// on vérifie si max par semaine atteint si c'est le cas on supprime la resa if (moment(createdItem.date).isSame(new Date(), 'week')) { createdItem.destroy().then(function() { request.flash('danger', 'Total de réservation maximum par semaine atteint'); response.redirect('/user/__show'); }); } // dans le cas d'un abonnement trouvé on touche pas aux cartes else if (findedRpaUserServiceSub) { request.flash('success', 'Réservation ajoutée'); response.redirect('/user/__show'); } // si on trouve une carte mais sans abonnement else if (findedRpaUserServiceCard) { if ((findedRpaUserServiceCard.remaining_services - 1) === 0) { findedRpaUserServiceCard.destroy().then(function() { request.flash('success', 'Réservation ajoutée'); response.redirect('/user/__show'); }); } else { findedRpaUserServiceCard.update({ remaining_services: findedRpaUserServiceCard.remaining_services - 1 }).then(function() { request.flash('success', 'Réservation ajoutée'); response.redirect('/user/__show'); }); } } else { // something else } 

You can also add a return inside each if to stop further processing or use next() if you are using expressjs to go to the next middleware.