She married Lionel Percival Mawhood (1888–1935) at the District of St Martin, London in September Quarter 1915; they had two children. Following Mawhood's death in 1935, she never remarried.

Mary Clare Absalom was born in 1892, the second of five daughters, to George Alfred Absalom and Annie Louise Austin. Mary Absalom first worked in an office but a loan of £50 allowed her to train at a dramatic school and she began her thespian career as Mary Clare on the London stage at the age of 18 in 1910; following which she spent two years touring the provinces to appear back in London in "A Posy on a Ring" at the Earl's Court Exhibition Theatre. She made her London West End debut in Turandot at the St. James Theatre in 1913, following which she appeared in many West End productions.

In films, she was mainly a character Actress, in later life often portraying mature ladies who had strength of character or were autocratic. She appeared in several silent films including the film The Black Spider in 1920, and thereafter divided her time between the stage and the cinema. In April 1927, she appeared in Packing Up, a short film produced in the DeForest Phonofilm sound-on-film process; the short featured Malcolm Keen and was directed by Miles Mander. Her first major sound film was in the 1931 Hindle Wakes, as Mrs Jeffcote; a role which she was to repeat in the 1952 remake.

In the theatre, she became one of Noël Coward's "leading ladies" appearing in several of his plays, in particular, Cavalcade in 1931. In September 1936 she played the leading role in the play Laura Garnett, by Leslie and Sewell Stokes, at the Arts Theatre Club, London and played the lead role of the victim in Agatha Christie's 1945 play Appointment with Death. In 1960, she appeared in Noël Coward's 50th play Waiting in the Wings with Sybil Thorndike.

In 1938, she was featured opposite Robert Donat and Rosalind Russell in The Citadel. She appeared in two of the British-made Alfred Hitchcock films, Young and Innocent, (1937) playing a nightmare of an aunt who demands that everyone enjoy themselves at her young daughter's birthday party, and The Lady Vanishes, (1938) in which she played a sinister baroness; two vastly different characters. She played the part of Linda Sanger in two different versions of The Constant Nymph and had previously been in the stage version.

Whilst Mary Clare played many leading roles, her only "title" role was as the very eccentric detective Palmyra Pym in the 1940 film Mrs Pym of Scotland Yard that also featured Nigel Patrick and Irene Handl.

In 1956, she was in several TV episodes in British television.