Her parents, Robert and Úna Brennan, both from County Wexford, were Republicans and were deeply involved in the Irish political and cultural struggles of the early twentieth century.

In her story The Day We Got Our Own Back she recounts her memory of how, when she was five, her home was raided by Free State forces looking for her father, who was on the run.

In it, Mary Ramsay, a "garrulous, greedy heap of a woman" tries to keep her job as a ladies' room attendant in a Dublin hotel.

[citation needed] Her career didn't really take off until after her death which led many of her stories to be reintroduced to the public and many articles written about her up until her passing.

[citation needed] She died of a heart attack on 1 November 1993, aged 76, and is buried in Queens, New York City.

[citation needed] Brennan's writing in her "Long-Winded Lady" pieces and in her short stories are quite different both in style and content.

In these stories she is an observer eavesdropping on strangers' conversations in bars, diners, hotel lobbies, and streets in places like Times Square and Greenwich Village.

In the final Derdon story, "The Drowned Man", Rose has died and Hubert has to pretend that he is overwhelmed with grief for his dead wife, "... she was gone, she had been good, and he wished he could miss her."

The main themes in Brennan's short stories are feelings of loneliness, vulnerability, despair, spite, and fear.

Brennan also wrote stories set in or around Manhattan, which she described as "the capsized city—half-capsized, anyway, with the inhabitants hanging on, most of them still able to laugh as they cling to the island that is their life's predicament."

Brennan's stories about her cats, dog and Long Island beach cottage show her mistrust of human nature and love of solitude and innocence.

Brennan wrote a novella, The Visitor, in the 1940s, but it was not published until 2000, after the only known copy of the manuscript was discovered in the archives of the University of Notre Dame.

In 1987, Mary Hawthorne, who was then on the staff of The New Yorker, grew interested in Brennan after seeing an older woman, dishevelled and dressed eccentrically, staring at the floor in the vestibule of the offices one day.

She began asking around about her, interviewing colleagues, among them William Keepers Maxwell Jr., Alastair Reid, Brendan Gill, and Gardner Botsford; family members; and Karl Bissinger, who had photographed her in her glamorous youth.

The same year, Christopher Carduff, an editor at Houghton Mifflin, published both a new, larger, collection of Brennan's "Long-Winded Lady" pieces and The Springs of Affection, a volume of her short stories.

In it, Bourke speculates that Brennan may have been the inspiration for the character Holly Golightly in Truman Capote's novella Breakfast at Tiffany's (1958).

In 2016, the Irish literary magazine and publisher The Stinging Fly republished The Springs of Affection with an introduction by Anne Enright.

In 2021 Brennan was included in the anthology "All Strangers Here", a collection of writing by authors who lived in Department of Foreign Affairs (Ireland) missions abroad (either as diplomats or their family members).

On 6 January 2024, a commemorative plaque was unveiled to honour Maeve Brennan at 48 Cherryfield Avenue, Ranelagh, Dublin, her "memory palace", where she lived from 1921, aged four until her family moved to America in 1934.

[7] On 25 January 2024, The Long-Winded Lady, a collection of Brennan’s New Yorker columns, written from the 1950s to early 1980s, introduced by Sinéad Gleeson, will be published.