An Italian village, early 19th century. While peasants rest from work, Nemorino, a young villager, watches the beautiful farm owner Adina reading a book. He loves her but feels she is beyond his reach (“Quanto è bella”). The peasants ask Adina what her book is about, and she tells them the story of how Tristan won the heart of Isolde by drinking a magic love potion (“Della crudele Isotta”). A drum roll announces the arrival of Sergeant Belcore and his men. He presents flowers to Adina and asks her to marry him (“Come Paride vezzoso”). Adina declares that she is no hurry to make up her mind but promises to think over the offer. Left alone with Nemorino, Adina tells him that his time would be better spent looking after his sick uncle than hoping to win her love. Even though he is kind and modest, she says she feels nothing for him (Duet: “Chiedi all’aura lusinghiera”).
Dr. Dulcamara, a traveling quack and charlatan, arrives in the village, advertising a potion capable of curing anything (“Udite, udite, o rustici”). When the doctor has finished his routine, Nemorino shyly asks if he sells the elixir of love described in Adina’s book. Dulcamara claims he does and pulls out a bottle of Bordeaux (Duet: “Obbligato, ah sì! obbligato!”). Though it costs him his last cent, Nemorino buys it and immediately drinks it, but Dulcamara explains that he has to wait until the next day for results (by which time Dulcamara will be gone). When Adina appears, Nemorino begins to feel the effect of the “potion.” Certain he will be irresistible to her the next day, he feigns indifference (Duet: “Esulti pur la barbara”). To punish him, Adina flirts with Belcore. The sergeant has been informed that he must return to his garrison, and Adina agrees to marry him at once. Shocked, Nemorino begs her to wait one more day, but she ignores him and invites the entire village to her wedding. Nemorino desperately calls for the doctor’s help.
At the pre-wedding feast in her farmhouse, Adina wonders why Nemorino is not present. When the notary arrives, she declares she will not sign the marriage contract until he appears. Meanwhile, Nemorino asks Dulcamara for another bottle of the elixir. Since he doesn’t have any money, the doctor agrees to wait at the inn for an hour so Nemorino can borrow the cash from someone. Belcore is annoyed that Adina has postponed the wedding. When Nemorino tells him that he needs money right away, the sergeant persuades him to join the army to receive a volunteer bonus of 20 scudi (Duet: “Venti scudi”).
Having bought more wine, Nemorino returns to find himself besieged by a group of girls. Unaware of the news that his uncle has died and left him a fortune, he believes the elixir is finally taking effect. Adina enters, feeling responsible for Nemorino’s enlistment, but when she sees him with the other girls, she reacts jealously (Quartet: “Dell’elisir mirabile”). Nemorino and the girls leave, and Dulcamara boasts to Adina about the power of his elixir, offering to sell her some as well. She replies that she will win Nemorino back on her own terms.
Nemorino, having noticed a tear on Adina’s cheek when she saw him with the girls, feels sure that she cares for him (“Una furtiva lagrima”). When she returns to tell him that she has bought back his enlistment papers, he again feigns indifference. Finally, she confesses she loves him. Belcore appears to find the two arm in arm but takes the situation with good humor, declaring that thousands of women await him elsewhere. Dulcamara reveals to the crowd the news of Nemorino’s inheritance and brags about how his miraculous potion can make people fall in love and even turn poor peasants into millionaires.