Born in 1896 in Leeds, Phyllis Barton (Matthewman) was the daughter of insurance manager Thomas Barton, and his wife, Ada Mary Pollard. She attended Leeds High School, but was prevented from seeking a higher education by the premature death of her father. Married to Sydney Matthewman in 1930, she lived with him in Leeds, Tottenham, Hindhead, Gosport and Merstham (Surrey), taking a position as a secretary when he had a breakdown. It was at this point that Matthewman began to write, aided by Sidney, who often helped with her plotting and characterization.
Matthewman was acquainted with celebrated school story author Elinor M. Brent-Dyer, through her aunt, and when Sydney Matthewman set up a literary agency in the late 1940s, Brent-Dyer became a client. From 1964 to 1969, when Brent-Dyer died, the Matthewmans lived with her in a joint establishment in Redhill. Phyllis Matthewman herself died in 1979.