Dorothy Roberts McCann, 63, a secretary on the staff of John F. Kennedy during his years in the Senate and White House, died at her home in St. Augustine, Fla., Monday following heart attack.

Mrs. McCann joined Kennedy's staff when he became a senator in 1953, and remained with him when he became president in 1961. She stayed in the White House under President Lyndon B. Johnson until her retirement in 1968 with 34 years of government service.

Mrs. McCann was born in Lawrence, Mass. She came to Washington in 1934 and worked for the Agriculture Department for four years before moving to Capitol Hill in 1938. She started there as a secretary on the staff of Sen. Ernest MacFarland (D-Ariz.).

In 1974, Mrs. McCann and her husband, William J., a retired official of the General Services Administration, moved from District Heights to St. Augustine. Mrs. McCann had been a member of the Mount Calvary Catholic Church in District Heights.

In addition to her husband, of the home in St. Augustine, survivors include three sons, Thomas, of Oxon Hill, and Dennis and Richard, both of Alexandria; three sisters, Evelyn Roberts, of Lawrenre, Madalene Donovan, of North Andover, Mass., and Mildred Crowley, of Hampton Hills, N.H., and two grandchildren