She attended Oxford University before working for Newsweek, The Observer, and The Sunday Times in London.
In 1967, she gave up her career in journalism to marry theatre critic Kenneth Tynan (1927–80).
She later wrote a screenplay based on Louise Brooks' autobiography Lulu in Hollywood, but this film never was made.
Kathleen Tynan was mentioned in Helen Fielding's 1996 novel Bridget Jones's Diary: "I read in an article that Kathleen Tynan, late wife of the late Kenneth, had 'inner poise' and, when writing, was to be found immaculately dressed, sitting at a small table in the center of the room sipping at a glass of chilled white wine", that information coming from Tynan's obituary by Joan Juliet Buck.
[1] In the television film Kenneth Tynan: In Praise of Hardcore (2005), she was portrayed by Catherine McCormack.