The novella follows the story of an unnamed narrator and his fascinating neighbor, Holly Golightly, over the course of a year in New York City.
The narrator, an aspiring writer, becomes intrigued by the charming and eccentric Holly, who lives by her wits and socializes with wealthy men. Holly is a teenage runaway who reinvented herself as a free-spirited socialite, visiting Tiffany's jewelry store as a refuge from her anxieties. She makes a living by accepting money from her gentlemen companions and delivering coded messages to the jailed mobster Sally Tomato.
Holly hosts lavish parties attended by various characters, including a Hollywood agent, a millionaire, and an eccentric model. Despite her carefree facade, Holly keeps secrets about her past, including a brief teenage marriage to a man named Doc Golightly. As the narrator gets to know Holly better, he becomes infatuated with her and they develop a close friendship.
However, Holly's inner circle crumbles when her friends suspect her of infidelity. The arrival of Doc Golightly also disrupts Holly’s new life, as he reveals Holly's real name is Lulamae Barnes and recounts their marriage when she was just 14 after she had run away from an abusive home. In the end, Holly decides to leave for Brazil but has a change of heart, reuniting with the narrator in a poignant conclusion.