Algernon Moncrieff and his friend Earnest Worthing one day discover that they both partake in the hobby of leading a double life. Algernon reveals that he enjoys escaping meaningless social obligations to become Mr. Bunbury, a rugged playboy who lives in the city.
Earnest reveals that he is “Jack in the country and Earnest in the city”, the former being his true identity. He confides in Algernon about his responsibility as the caretaker of a young woman, and his intentions to end his double life in order to settle down with Gwendolen Fairfax, Algernon’s cousin and Jacks lover. Later, when Gwendolen and her mother, Lady Bracknell, join their company Jack confesses his love and proposes to her. It is then that she reveals she loves Jack entirely for his alias name and will only marry a man named Earnest. This, combined with Lady Bracknell’s disapproval of his mysterious past, motivate Jack to hightail it to the country where he plans to put an end to his double life and christen himself with the name Earnest. Algernon meanwhile takes interest in the ward Jack mentioned earlier and makes up his mind to appear before her as Earnest.
Algernon, unbeknownst to Jack, arrives at the estate where he meets Cecily Cardew, the ward, and Miss Prisim, her teacher. Cecily knows ‘Earnest’ to be Jack’s troublesome brother and is pleased to finally meet the man she’s been dreaming about. The two fall for each other and Algernon, posing as Earnest, proposes. Cecily reveals that she too will only marry a man named Earnest, causing Algernon to make plans for a rechristening.
Meanwhile, Jack has arrived at the country estate with the news of Earnest’s death. However, his attempt to end his double life fails when Algernon reveals himself. For fear of exposing his lies, Jack partakes in the charade.
Gwendolen at this point makes a surprise visit to Jack’s estate. While waiting to see Jack, she meets Cecily and the two talk over tea. A fight erupts when the women discover they’re both engaged to a man named Earnest. Algernon and Jack arrive at this scene and are forced to reveal their lies; however, all is forgiven when the men reveal that they both have planned to be christened with the name Earnest.
At this point Lady Bracknell arrives at the estate in search of her daughter. Having come upon the baffling scene of lovers, she expresses her disapproval of anyone’s union. When she learns that Miss Prisim is present at the estate however, she seems to recant her statement. Its revealed that Miss Prisim was entrusted with Lady Bracknell’s sister’s child 28 years prior and lost him at a train station. The child turns out to be Jack, making Algernon his brother, and Lady Bracknell his aunt. Upon inquiring his true Christian name Jack learns, after much commotion, that he was named for his father, Ernest.
His lies become the truth, as his name truly is Ernst and he really does have a brother in the city. The couples embrace, and the play closes with Jack exclaiming that he has learned “the importance of being Earnest”.