The village folk gather as Adina, a beautiful landowner, reads aloud from a book. The young peasant Nemorino is in love with her. Sergeant Belcore arrives with his regiment and his eye falls on Adina. Adina is indifferent to Nemorino's interest. The quack doctor Dulcamara sells Nemorino a love elixir and says it will not take effect until the next day; the bottle contains only wine. The Sergeant returns. He has received orders to take his troops to a new location, and so proposes to Adina that they marry before the day is out. Nemorino worries that the elixir will not have time to work, and entreats them to wait one more day. This gets a cursing from Belcore. Adina invites all to a banquet, while Nemorino goes alone to seek the doctor's help.
At a pre-wedding celebration for Adina and the Sergeant. Adina is sad to see that Nemorino is absent. Nemorino has joined Belcore's regiment as a means to earn the money for another bottle of the elixir. Gianetta arrives with news that Nemorino's uncle has died and willed him a fortune. Nemorino himself arrives soon after, and as the young women suddenly shower him with attention, Nemorino believes the elixir is working. Adina tries to win Nemorino back. Seeing this, Nemorino becomes aware of her feelings and sings his famous aria, Una furtiva lagrima (A furtive tear). Adina has bought back Nemorino's military contract from Belcore and gives it to him; Nemorino exclaims that if he is not loved, he might as well go off to die as a soldier. The two confess their true feelings for each other. Belcore returns, and lets go of Adina with good grace. As Dulcamara leaves the village, a crowd gathers to give him a rousing farewell.