King Ferdinand of Navarre and his three closest lords – Biron, Dumain, and Longaville – have taken a vow of abstinence from the sensual pleasures of life to devote three years to the pursuit of knowledge. This task will involve isolating themselves in the court with extreme limitation upon contact with ladies. The only one of the four exhibiting doubt about the plan is Biron, but finally he too signs the oath. Meanwhile, the Princess of France has arrived in Navarre.
Constable Dull arrives with news about a criminal act by a man named Costard: flirting with an innocent country girl. Costard is punished for this transgression by Don Armado the enforcer.
The Princess arrives and is taken aback by the rather inhospitable treatment. The King and his lords arrive and each is instantly smitten with the Princess or one of her ladies. Biron pressures Costard into delivering a love letter to Rosaline, one of those ladies. Costard has also become the messenger for a letter from Don Armado to lady Jaquenetta. Costard gets the letters confused and winds up delivering them to the wrong women.
This mistake results in some comical confusions regarding who loves whom and numerous remarks from Biron, who felt the whole premise of trying to spend three years studying without giving into the temptations of the flesh was hopelessly doomed from the beginning. Soon, the men attempt to disguise themselves as Russians in order to play a trick upon the women, but the women are too cunning and after discovering their plans beforehand, set about making sure each lord sets to wooing the intended object of his affection.
The fluffy tone of light banter and clever repartee suddenly changes when news arrives for the Princess that her father has died. They women prepare to head back to France amid affirmations of sincerity from the men. An agreement is made that if they men are really serious, they must profess their love one year later, at which point the ladies are free to accept their marriage proposals.
