Margaret M. Barker, 84, a retired real estate sales agent and a former teacher in the D.C. public schools, died of pneumonia Tuesday at the Wisconsin Avenue Nursing Home.

Mrs. Barker was born in Central City, Neb., and graduated from Grand Island Baptist College in Nebraska. She came to Washington during World War I and worked in the Office of War Risk Insurance. About 1920, she married Howard F. Barker, who later became an official of the U.S. Tariff Commission, and spent most of the rest of her life in this area.

In the 1930s and up until 1947, Mrs. Barker was a teacher of mathematics and social studies in the D.C. schools. Among the places she taught were Hine and Jefferson junior high schools. In all, she had 13 years of service.

In 1947, she began selling real estate in Northwest Washington and Montgomery County.She retired in 1967, having spent most of those years with the firm of Legum and Norman, now Legum and Gerger.

Her husband died in 1960.

Mrs. Barker's survivors include two daughters, Katherine McClenon, of Washington, and Ruth Barker, of Arlington; a sister, Ruth Carlson, of Summer, Md., and three grandchildren.

The family suggest that expressions of sympathy be in the form of contributions to the Barker Memorial Fund at the Cleveland Park Congregational United Church of Christ, where Mrs. Barker was a member of the Board of Deacons, at 3400 Lowell St. NW, Washington, D.C., 20016. CAPTION: Picture, MARGARET M. BARKER