[1][2] Mullett began his career in 1954 at the United Mutual Life Insurance Company in New York City, where he rose through the ranks to become vice president and assistant treasurer.
He worked briefly as a cost analyst at the Equitable Assurance Company of America from 1962 to 1963 before transitioning to higher education administration, returning to Lincoln University in 1963 to serve as assistant to the vice president of fiscal affairs, comptroller, business manager, and (starting in 1969) vice president of fiscal affairs and treasurer.
[2] He served as Lincoln University's interim president from July 1, 1985, to February 1, 1987, succeeding the retiring Herman Branson and stepping aside upon the inauguration of Niara Sudarkasa.
[3] Mullett left Lincoln in 1989 to serve as vice president of finance and fiscal affairs at Texas Southern University.
He served as vice president of fiscal affairs at Jarvis Christian College from 1990 to 1993.