The King of Navarre and his companions—the lords Berowne, Longaville, and Dumaine—swear an oath in which they commit to three years of study while fasting, sleeping minimally, and avoiding all contact with women. Both Longaville and Dumaine agree to the oath quickly, but Berowne holds out, questioning the wisdom of neglecting the young men’s baser instincts, which will most likely cause them each to break their oath. He also points out that the King will have to break his oath when the Princess of France makes her scheduled visit to court. The King agrees to make an exception for the Princess, and Berowne agrees to swear the oath.
During the debate about the oath, the King receives a letter from Don Armado, a Spaniard visiting the King’s court, informing him that he has caught Costard, a fool, and Jaquenetta, a country maid, consorting in the park. The King sentences Costard to imprisonment with minimal rations, and he and his lords withdraw to begin their scholarly sequestration.
Meanwhile, Armado confesses to Mote, his page, that he has fallen in love with Jaquenetta. He writes her a letter that he asks Costard to deliver. Soon thereafter, the Princess of France arrives to visit the King. However, because of his oath, the King only agrees to meet her if she and her attending ladies set up their camp outside the city gates. Immediately upon meeting her, the King falls in love with the Princess. Likewise, the three lords fall in love with the three ladies: Berowne fancies Rosaline, Longaville fancies Maria, and Dumaine fancies Katherine.
Soon after their initial meeting, Berowne writes a love letter to Rosaline and employs Costard to deliver it. However, Costard, who has not yet delivered Armado’s letter to Jaquenetta, accidentally switches the letters and misdelivers both. When he gives Berowne’s letter to Jaquenetta, she brings it to the schoolmaster Holofernes and the curate Nathaniel to read for her. They explain that the letter was meant for someone else, and, suspecting something treasonous afoot, they instruct her to deliver it to the King.
Meanwhile, Berowne writes a love poem for Rosaline and reads it aloud to himself. He hears the King approaching and hides. From his hiding spot, he listens as the King reads a poem he wrote for the Princess. Next, the King hides as Longaville approaches and reads his poem for Maria. Finally, Dumaine enters, Longaville hides, and all three concealed lords hear Dumaine read an ode he has written to Katherine. Longaville advances and tells Dumaine that he is not alone in love. The King then comes forward and scolds the two men for breaking their oath. Berowne emerges next and, revealing that the King is in love as well, chides all three for their perjury. Just then, Jaquenetta arrives with the love letter Berowne wrote for Rosaline. He attempts to tear the letter up, but Dumaine recognizes Berowne’s signature, which forces him to confess that he, too, is in love. The four men then make a new vow to court their beloveds.
On the advice of Holofernes, the King and his lords plan a pageant that will feature the Nine Worthies. But before the masquerade, they decide to visit the Princess’s pavilion disguised as Russians. Boyet runs ahead to warn the Princess and her ladies of the charade. The ladies decide to beat the lords at their own game by donning masks and exchanging the gifts the lords have sent them. Their plan works, and the lords mistake them for each other. After the men leave and reappear as themselves, the women reveal their prank.
Chastened by the ladies’ mockery, the King wishes to stop the pageant of the Nine Worthies, but Berowne convinces him to allow the performance to proceed. However, instead of taking it seriously, he and the other lords heckle the performers, attempting to match the ladies in their mockery.
The heckling doesn’t impress the ladies, who feel bad for the incompetent commoners who’ve been roped into performing. The pageant is then interrupted by a message that the Princess’s father, the King of France, has died. The lords try to convince the ladies to marry them before they return to France, but the women tell their suitors to seek them again in a year’s time. The play ends with their departure.