Mickens returned to Fisk University as a faculty member in 1970 and later worked at the Joint Institute for Laboratory Astrophysics, from which he was recruited to what was then Atlanta University in 1981. He became a Callaway Professor in 1986. Mickens was elected a Fellow of the American Physical Society in 1999, with the citation "For his sustained service to the physics community and his original contributions on the applications of mathematics to the study of physical systems."