At the beginning of 1364, after the failure of the negotiations of Évran, Montfort, with the assistance of John Chandos, came to attack Auray, which had been in the hands of Franco-Bretons since 1342. He entered the town of Auray and besieged the castle, which was blockaded by sea by the ships of Nicolas Bouchart coming from Le Croisic.

The battle began with a short skirmish between the French arbalesters and the English archers. Each Anglo-Breton corps was attacked head on, one after the other, but the reserves restored the situation. The right wing of the Franco-Breton position was then counterattacked and driven back and since it was not being supported by its own reserves, it was folded up towards the centre. The left wing then folded in turn, the Count of Auxerre was captured, and the troops of Charles of Blois broke and fled. Charles, having been struck down by a lance, was finished off by an English soldier, obeying orders to show no quarter. Du Guesclin, having broken all his weapons, was obliged to surrender to the English commander Chandos. Du Guesclin was taken into custody and ransomed by Charles V for 100,000 francs.

This victory put an end to the war of succession. One Year later, in 1365, under the first Treaty of Guérande, the king of France recognized John IV, the son of John of Montfort as duke of Brittany.