Kate Jennings grew up on a farm near Griffith, New South Wales. While earning a Bachelor of Arts with Honours from the University of Sydney during the late 1960s and early 1970s, Jennings was active in left-wing politics and feminism, later editing Mother I'm Rooted (1975), a collection of contemporary women's poetry. In 1975, Jennings published her first collection of her own poems, Come to Me My Melancholy Baby, exploring the trials of being a feminist poet in the 1970s. Jennings left Australia for New York in 1979 where she worked as a writer, editor, and speechwriter for a major investment bank .
Jennings wrote short stories, essays, poetry and novels and, in 1993, began a period as poetry editor for the Bulletin. Jennings's essays ranged over a variety of topics, but her critiques of Australian literature and feminism were not always been well received in Australia. Jennings's personal prose and essay collections include Save Me, Joe Louis (1988) and Bad Manners (1993).
Some of Jennings's short stories explore her childhood in the Riverina; she extended this exploration with the novel Snake (1996), attracting praise from writers such as Jill Ker Conway and Shirley Hazzard. Her second collection of poetry, Cats, Dogs and Pitchforks (1993), also attracted wide admiration. In 2002, Jennings published Moral Hazard, a novel set in New York, drawing on her experience as a speechwriter and her husband's battle with Alzheimer's disease. The novel won several prizes including the Australian Literature Society Gold Medal. Jennings's memoir Stanley and Sophie was published in 2008. Her 2010 publication Trouble: Evolution of a Radical: Selected Writings 1970-2010 is described by her publisher as an 'unconventional autobiography and a record of remarkable times'; it traces the various trajectories of Jennings's life over four decades.
Jennings presented the second Ray Mathew Lecture at the National Library of Australia, 29 June 2010. The lecture is presented annually by an Australian writer living overseas.
Jennings died in New York in May 2021.