Mirjam Tuominen was born in Kajana and grew up in a middle-class family in Helsinki in an atmosphere very much characterised by the early death of her father. She graduated and after the war divorced her artist husband Torsten Korsström. With her income as a writer and critic, she managed to provide modest living conditions for herself and her two daughters. After a mental breakdown in the 1950s, she converted to Catholicism.
She made her debut in 1938 with Tidig tvekan (SS) and in her subsequent short story collections Murar, 1939, and Mörka gudar, 1944, described the female psyche, guilt, and fear, while Visshet (SS) of 1942 is about the witch hunts and the violence of the Nazis. With her insistence on innovative artistic expression, her works are at the centre of wartime Finnish modernism. She continued her analysis of violence in her confessional book Besk brygd, 1947. In the 1950s she published confessional poetry and in 1961 the religious meditation book Gud är närvarande.
Mirjam Tuominen's earlier writing was well-received, while her subsequent books were not understood, and her later Catholic poems were rejected by the publishers. In the 1980s and 1990s she was again successful with a three-volume selection of short stories and poems.