As the play begins, the Stage-keeper delivers a brief introduction. A different writer, he says, could have created a much more exciting work, but this one (Jonson) would not listen to the more experienced man’s advice.

[S]ome writer that I know had had but the penning o’ this matter, he would have made you such a jig-a-jog in the booths, you should have thought an earthquake had been in the Fair! But these master poets, they will have their own absurd courses; they will be informed of nothing.

A Scrivener enters and reads a lengthy contract for the audience’s agreement, indicating that they will exercise their free will to like or dislike the play and not be unduly swayed by another’s opinion: “not censure by contagion . . . from another’s voice.”

Jonson both establishes an intricate plot and makes the characters’ dialogue hard to deliver by using names that are puns on the characters’ personalities or roles in the play. Quarlous, for example, is quarrelsome. Winwife has set out to do exactly that: win a wife. Littlewit has little success in deciphering the other men's motives, because he is not smart. Once the plot is established, Littlewit’s summation of what has occurred so far comes out as a jumble of words. As he attempts to explain why Winwife is pursuing his mother-in-law, a much older woman, as a bride, he urges his wife—whose first name is Win—not to be shy about letting the other men kiss her.

[M]aster Quarlous is an honest gentleman, and our worshipful good friend, Win; and he is master Winwife’s friend too: and master Winwife comes a suitor to your mother, Win; as I told you before, Win, and may perhaps be our father, Win: they’ll do you no harm, Win; they are both our worshipful good friends. Master Quarlous! you must know master Quarlous, Win; you must not quarrel with master Quarlous, Win.

Young Bartholomew Cokes finds himself torn between two desires when he sets out for the fair (which appeals to him because it bears his name). He arrives with his servant, Humphrey Waspe, whom he calls Numps. Bartholomew intends to maximize his commercial opportunities but also aims to entertain his beloved, Grace Wellborn. As her name indicates, she is of higher status, which is reflected in her superior attitude. Grace tells him that she is not impressed by the fair.

Cokes: Well, Numps, I am now for another piece of business more, the Fair, Numps, and then—

Waspe: Bless me! deliver me! help, hold me! the Fair!

Cokes: Nay, never fidge up and down, Numps, and vex itself. I am resolute Bartholomew in this; I’ll make no suit on’t to you; ’twas all the end of my journey indeed, to shew mistress Grace my Fair. I call it my Fair, because of Bartholomew: you know my name is Bartholomew, and Bartholomew Fair . . .

Grace: Truly, I have no such fancy to the Fair, nor ambition to see it: there’s none goes thither of any quality or fashion.

Cokes: O Lord, sir! you shall pardon me, mistress Grace, we are enow of ourselves to make it a fashion; and for qualities, let Numps alone, he’ll find qualities.

Bartholomew’s trusting nature, combined with his tendency to show off, or act the “cockscomb” as Waspe calls it, lands him in deep trouble. At the fair, he encounters a ballad-singer called Nightingale, who charms the young man with a lengthy song about cut-purses (pickpockets). Bartholomew praises his cleverness, sings along with him, and dances merrily. Despite Numps’s warnings, he also pulls out his own purse to make a wager, thus calling attention to his having plenty of money. Nightingale’s accomplice, Edgworth, soon joins the fun and steals Bartholomew’s purse.

Night: Youth, youth, thou had’st better been starved by thy nurse,
Than live to be hanged for cutting a purse.

Cokes: That again, good ballad-man, that again. [He sings the burden with him.] O rare! I would fain rub mine elbow now, but I dare not pull out my hand.—On, I pray thee; he that made this ballad shall be poet to my masque . . . [sings after him.] Youth, youth, etc.—Pray thee, stay a little, friend. Yet o’ thy conscience, Numps, speak, is there any harm in this?

Waspe: To tell you true, ’tis too good for you, less you had grace to follow it.

Cokes: Youth, youth, etc.; where’s this youth now? a man must call upon him for his own good, and yet he will not appear. Look here, here’s for him; handy dandy, which hand will he have? On, I pray thee, with the rest; I do hear of him, but I cannot see him, this master youth, the cut-purse.