Brant Royle buys and sells tobacco, building a cigarette manufacturing empire, but his empire is starting to crumble. He is romantically drawn to the daughter of the tycoon who had earlier brought ruin to his family, and she may have an agenda of her own.

Young at Heart is centered on a family headed by a music-loving patriarch and his musically inclined daughters looking for romance. Doris Day plays the youngest daughter. Laurie, and Gig Young plays Alex Burke, a likable composer who comes for an extended visit and eventually wins the hearts of all three sisters. Frank Sinatra plays Barney Sloan, a cynical songwriter hired by Alex to do arrangements for an upcoming Broadway show.