Born Marie Anne Boland in Philadelphia, Pennsylvania, she was the daughter of an actor and was performing on stage by the age of fifteen. She debuted on Broadway in 1907 and had appeared in eleven Broadway productions before making her silent film debut for Kay-Bee Pictures in 1915. After appearing in nine movies, she left filmmaking in 1920, devoting herself to the stage and appearing in a number of Broadway productions. Her greatest success on the stage in the 1920's was the comedy The Cradle Snatchers (1925-26) in which she and Edna May Oliver, abandoned by their husbands, taken on young lovers, Boland's paramour being Humphrey Bogart in one of his first roles.

After an eleven year absence, in 1931 she was lured back to Hollywood by Paramount Pictures, attracted by the fact that all films were then being made with sound. She achieved far greater film success with her second try, becoming one of the 1930's most popular character actresses, always playing major roles in her films and often starring, notably in a series of comedies opposite Charles Ruggles. Of her film work, the 1935 production Ruggles of Red Gap is probably the most noted. However, she is likely best remembered for her role as Countess DeLave in the 1939 film The Women and that of Mrs. Bennet in 1940s Pride and Prejudice. Although she performed in another forty-nine films and later television productions, Boland also continued to work in live theatre, making her last Broadway appearance in 1954 at the age of seventy-four. That play, Lullaby, was not a success. Her last acting was done in the 1955 television adaption of The Women recreating her film role. For her contribution to the motion picture industry, Mary Boland has a star on the Hollywood Walk of Fame at 6150 Hollywood Blvd.

In 1965, Mary Boland died as the result of a heart attack and was interred in the Great Mausoleum, Sanctuary of Vespers in Forest Lawn Memorial Park Cemetery in Glendale, California.