Hello, Dolly! tells the story of Dolly Gallagher Levi, a widow living hand-to-mouth in New York City in the 1890s. Dolly finds various types of work to get by, including as a matchmaker. At the start of the show, she is engaged as a matchmaker in finding a second wife for a wealthy widower, Horace Vandergelder, who lives in Yonkers, where he owns a Hay and Feed Store.
Over the course of 24 hours, thanks in part to Dolly's machinations and thanks in part to coincidence and serendipity, several developments occur that lead us to a happy ending:
- Vandergelder's clerks. Cornelius and Barnaby, take a trip to New York City, where Cornelius meets and falls in love with Irene Molloy, the young widow whom Dolly had earlier introduced to Vandergelder as a possible second wife.
- Vandergelder agrees to make Cornelius a partner in his Hay and Feed store.
- After having tried to prevent it, Vandergelder agrees to allow his niece, Ermengarde, to marry Ambrose Kemper, a poor artist with whom she's in love
- And Vandergelder realizes that Dolly herself is the right woman to be his second wife, which had been Dolly's plan all along.