In the country village of Windsor, Justice Shallow and his nephew Slender complain to Parson Evans that Sir John Falstaff (from Henry IV, parts 1 and 2) has wronged them. Further, he is pursuing the hand of Mistress Anne Page, who they feel Falstaff is not worthy to marry. Specifically, Slender accuses Falstaff of getting him drunk, then picking his purse. Falstaff, Bardolph, Nym, and Pistol all deny it. Slender, upon seeing Anne, falls in love. Parson Hugh Evans and Shallow suggest he tell her his affections and propose to her. He tries, but is overcome with shyness. Evans tells Simple (Slender's servant) to give a letter to Mistress Quickly, a friend of Anne's, asking her to tell Anne of Slender's desires for her. At the Garter Inn, Falstaff worries that he's running out of money, so he hires off his "friend" Bardolph as a bartender, then informs Pistol and Nym that he intends to sleep with Ford's wife and Page's wife, then steal money from them. Insulted, Nym and Pistol refuse to take part; further, they secretly decide to inform the women's husbands of Falstaff's intentions. At the French Doctor Caius' house, Quickly assures Simple that she will put in a good word for his master, Slender. Caius comes home and catches Simple there, admonishes Quickly, and sends a letter with Simple challenging Evans to a duel for playing matchmaker, since Caius himself wishes to marry Anne. Caius and Simple leave and Fenton arrives, also asking for Quickly's assurance that she'll put in a good word for him to Anne.
Mrs. Ford and Mrs. Page receive Falstaff's letters, compare them, and find them to be identical. They, along with Quickly, plot their revenge on Falstaff for being so bold. Pistol and Nym warn Mr. Page and Mr. Ford of Falstaff's intentions: Page trusts his wife to act appropriately, but Ford, always untrusting of his wife, convinces the innkeeper to call him Brooke, as a disguise, so that he may converse with Falstaff without him knowing Brooke is really Mr. Page. Shallow informs all that Evans and Caius will indeed duel. Quickly comes to Falstaff's room and tells him he can see Mrs. Ford between 10 and 11 am, but that Mrs. Page is more reluctant to see him and therefore deserves to have Falstaff's page, Robin, as a gift. Mr. Ford comes to Falstaff, disguised as Brooke. He offers Falstaff money if Falstaff will arrange for him (Brooke) to sleep with Mrs. Ford (in hopes of keeping Falstaff from doing it). Falstaff agrees and continues on to insult and degrade Mr. Ford (not knowing Brooke is Ford). In a field near Windsor, Caius, incensed, waits for Evans, who does not show.
Near Frogmore, Evans, also invigorated (yet nervous), waits for Caius. Caius begins wondering and they both meet and learn that the Host (the innkeeper) told them different locations so that they could not fight. They put aside their differences and vow to get him back for lying to them. At Ford's house, Falstaff shows up to woo Mrs. Ford. Mrs. Page then arrives pretending that Mr. Ford is coming to look for Falstaff. The women convince Falstaff to hide in a trunk, then have Mrs. Ford's servants take it to the Thames and dump it and Falstaff into the river. On their way out, Mr. Ford does indeed show up with other men. They search the house (but not the trunk) and cannot find Falstaff. At Page's house, Fenton promises his love to Anne. Yet, Mr. Page wants her to marry Slender while Mrs. Page wants her to marry Caius. Quickly, though divided, thinks Fenton is best for Anne. At Falstaff's room, Quickly informs him that Mrs. Ford will see him between 8 and 9 am. Ford (as Brooke) shows up and Falstaff tells him what happened and of his next encounter with Mrs. Ford. At Ford's house, Falstaff is again with Mrs. Ford. Again, Mrs. Page comes warning that Mr. Ford is coming (falsely, she believes). Again, he truly is. They decide to dress Falstaff as a woman. To chide Mr. Ford, they have the servants carry out the trunk again, but this time without Falstaff. Mr. Ford, thinking Falstaff to be a witch (his servant's aunt, whom he hates) beats Falstaff (as a she) and chases him out of the house. The wives decide to actually tell their husband's the truth of the proceedings. They all decide to have the wives meet Falstaff at an oak at midnight, then have children dressed as fairies scare him. Mr. Page plans to marry his daughter to Slender in the commotion. Similarly, Mrs. Page plans for Anne to marry Caius during the night. At the Garter Inn (Falstaff's room), Bardolph informs the Hose that three horses he rented to German lords have been stolen. Evans and Caius, behind the ruse, then separately warn the Host to not rent any horses to thieves posing as German Dukes. Evans and Caius pretend to not know they have already been "stolen". Fenton then convinces the Host to procure a priest to marry him and Anne that evening. Anne's father has told Slender she will be the only person in white at the midnight gathering; her mother has told Caius she'll be wearing green; in fact, she'll be wearing neither and will spy away with Fenton.
Falstaff meets Mrs. Ford and Mrs. Page at the oak at midnight. The fairies appear, scare off the women, and begin pinching and hitting Falstaff. Caius takes the fairy wearing green; Slender takes the one wearing white; and Fenton takes Anne. All the fairies depart and Mr. and Mrs. Page, Mr. and Mrs. Ford, and others appear to reveal to Falstaff that he is the butt of a practical joke. Unhappily, Mr. and Mrs. Page learn that neither Slender nor Caius married Anne. Instead, all learn of Anne and Fenton's elopement. All decide to accept the couple, forgive Falstaff, and go home and laugh about the preceding day's events.