The second act opens in Leonato's house, with the host and his family at supper. Leonato, Beatrice and Hero talk about Don John, whom they regard as melancholic and taciturn. Beatrice remarks that he is the extreme opposite of Benedick and states she would rather prefer a man mid-way between their two characters. Leonato warns his niece of becoming a spinster by being so overtly hostile towards men. However, Beatrice retorts that in her opinion, remaining single is actually a blessing. It may well please her cousin Hero to obey her father as to marrying, but she herself will never be "overmastered" by a man.
As Leonato reminds Hero of Don Pedro's plan to woo her, the prince, Claudio and Benedick enter wearing masks. The ball beginning, Don Pedro approaches Hero and asks her to walk a round with him, to which she agrees. They walk off, and Benedick moves up dancing with Beatrice, who cannot identify him through his mask. She complains vehemently to her dancing partner about Benedick, calling him "the prince's jester" and "a dull fool".
As the main party leaves, Don John, Borachio, both unmasked, and Claudio stay behind. Although he wears a mask, the two villians recognize him as Claudio and set forth in their plan to ruin his engagement to Hero. When Don John addresses him as Benedick, Claudio takes up the role and is told that Don Pedro is presently wooing Hero for himself and not for Claudio. Don John and Borachio insist that they heard the prince confessing his true intentions. Being alone, Claudio shows disappointment and cannot be cheered up by Benedick, who enters to tell him the good news of Don Pedro's orginal plan of wooing Hero for Claudio has succeeded.
Claudio leaves in distress and Benedick shortly meditates on Beatrice's low opinion of him, before Don Pedro enters to look for Claudio. Benedick tells him of the misunderstanding needing Don Pedro's resolution. When the topic of their conversation changes to Beatrice, Benedick readily assists that he would never under any circumstances marry such an insulting woman, and exits.
When Beatrice and Claudio enter, Don Pedro tells the latter that he had indeed not wanted Hero for himself. Leonato has given his consent to the marriage of Claudio and Hero, leaving the groom overgladly talking apart with his financée. Beatrice comments that she shall soon be the only woman without a husband, which prompts Don Pedro to ask her whether she might consider marrying him. She declines wittily and leaves. Don Pedro remarks to Leonato that she would be an excellent wife for Benedick, and intends to bring the two of them together. Hero and Leonato agree to help him.
In a room in Leonato's guest house, Don John grumbles at Claudio's upcoming marriage which he intends to cross once more. His follower Borachio comes up with an intrigue: since he is the lover of Hero's attendant Margaret, he plans to appear with her at Hero's window late at night, with Claudio and the other men watching the scene from below, mistaking Margaret for Hero being unfaithful to Claudio. Don John agrees on the idea and the two of them part to realise their plan.
Benedick appears, walking by himself in the garden, wondering at his friend Claudio's recent change from an ambitious soldier into a passionate lover. Although Benedick does not doubt that such a transformation might come over him as well, he resolves to defy love as long as he can. As he begins to name the qualities of his perfect wife, Don Pedro, Leonato, Claudio and the musician Balthasar appear. Benedick hides himself to overhear them.
After Balthasar has performed a song encouraging ladies not to deplore the fraud men by their nature exhibit, Don Pedro, aware of Benedick overhearing, asks Leonato if Hero has indeed said that Beatrice was in love with Benedick. Leonato confirms that Beatrice is even violently in love with him, although she treats him with disdain. Benedick cannot believe his ears, but Claudio also affirms that he knows of Beatrice's secret passion. The three men agree that it would be most unwise to let Benedick know, although they hold him to be of extraordinary character. Convinced that Benedick has taken the bait, they exit.
Benedick, being alone, tentatively allows himself to believe that Beatrice loves him. He is at once softened in his resolution to stay a bachelor and decides to observe her very closely. At once, Beatrice enters herself, delivering a message for him. Although she behaves scornfully once again, Benedick interprets her words as vows of love and admits having fallen in love with her, too.