It was in the 1930s that Melnea Cass began a lifetime of volunteer work on the local, state, and national level. She first contributed her services to the Robert Gould Shaw House, a settlement house and community center. She was the founder of the Kindergarten Mothers. Her community activities over the years were numerous and varied: Pansy Embroidery Club, Harriet Tubman Mothers' Club, and the Sojourner Truth Club, worked in the Northeastern Region of the National Association of Colored Women's Clubs as a secretary, helped form the Boston local of the Brotherhood of Sleeping Car Porters to name a few. During World War II she was one of the organizers of Women In Community Service, which later became Boston's sponsor of the Job Corps. In 1949 she was a founder and charter member of Freedom House, which was conceived by Muriel and Otto Snowden. A year later, Boston Mayor John Collins appointed her as the only female charter member to Action for Boston Community Development (ABCD), which assisted people who lost their homes to urban renewal efforts. From 1962 to 1964, Cass was president of the Boston branch of the National Association for the Advancement of Colored People (NAACP). From 1975 to 1976, Cass was chairperson for the Massachusetts Advisory Committee for the Elderly.