The third act opens on the promenade Cour-la-Reine in Paris, a scene of merry making where all the buying, selling and amusements of a great fair are going on.
The pretty ladies of the first act, Yavotte, Poussette and Rosette are being entertained by new lovers, while rich old Guillot looks in vain for a sweetheart.
Manon, who appears on de Brétigny's arm, is the queen of the festival. She has stifled the pangs of conscience which had troubled her when she left de Grieux, and her passion of jewels and riches is as insatiable as ever. Guillot, who hears that de Brétigny has refused to comply with her last wish, which is to order the ballet of the grand opera to dance in the open market-place for her own amusement, rushes off to pay for this whim himself, hoping thereby to gain the young lady's favour.
Manon slowly wanders about in search of new and pretty things to buy, while Brétigny suddenly finds himself face to face with the old count de Grieux. When he asks for news of his son, the count tells him, that the young man has renounced the world and become an Abbé and is a famous preacher at Saint Sulpice. He cuts de Brétigny's expressions of astonishment short by telling him, that this turn of things is due to de Brétigny's own conduct, meaning that the latter had done a bad turn to his friend by crossing his path in relation to a certain pretty young lady. De Brétigny indicating his lady-love by a gesture says: "That is Manon", and the count, perceiving her beauty quite understands his son's infatuation.
But Manon's quick ears have also caught bits of the conversation and beckoning to her lover she sends him away to buy a golden bracelet for her. She then approaches the count and asks him, if his son has quite overcome his passion for the lady whom she says was a friend of hers. The old man acknowledges, that his son had had a hard struggle with his love and grief but adds "one must try and forget" and Manon repeats the words and falls into a fit of sad musing.
Meanwhile Guillot has succeeded in bringing the ballet-dancers who perform a beautiful gavotte and other dances. When these are ended he turns to Manon in hope of a word of praise, but the wilful beauty only turns from him to order her carriage, which is to take her to Saint Sulpice, saying lightly to Guillot that she has not cared to look at the ballet after all.
The next scene takes place in the parlour of the seminary in Saint Sulpice. A crowd of ladies has assembled to praise the new Abbé's fine preaching. They at last disperse, when the young Abbé enters with downcast eyes. He is warmly greeted by his father, who has followed him. The father at first tries to persuade him to give up his newly chosen vocation before he finally takes the vows, but seeing him determined, the Count hands him over his mother's inheritage of 30,000 Lires [Transcriber's note: Livres?] and then bids him good-bye. The young man retires to find strength and forgetfulness in prayer.
When he returns to the parlour he finds Manon. She has also prayed fervently, that God would pardon her and help her to win back her lover's heart. A passionate scene ensues, in which Manon implores his forgiveness and is at last successful, De Grieux opens his arms to her and abandons his vocation.
The fourth act opens in the luxurious drawing-rooms of a great Paris Hotel. Games of hazard and lively conversation are going on everywhere. Manon arriving with de Grieux is joyously greeted by her old friends. She coaxes her lover to try his luck at play and is seconded by her cousin Lescaut, himself an inveterate gambler, who intimates that fortune always favours a beginner. Guillot offers to play with de Grieux, and truly fortune favours him. After a few turns, in which Guillot loses heavily, the latter rises accusing his partner of false play.
The Chevalier full of wrath is about to strike him, but the others hold him back and Guillot escapes, vowing vengeance. He soon returns with the police headed by the old Count de Grieux, to whom he denounces young de Grieux as a gambler and a cheat and points out Manon as his accomplice. Old Count de Grieux allows his son to be arrested, telling him he will soon be released. Poor Manon is seized by the guards, though all the spectators, touched by her youth and beauty beg for her release. The old Count says she only gets her deserts.