Apel was appointed lecturer at the University of Mainz in 1961. He was a full professor of philosophy at the University of Kiel from 1962 to 1969, at theUniversity of Saarbrücken from 1969 to 1972, and at the University of Frankfurt am Main from 1972 to 1990.^[4] In 1990 he transferred to emeritus status. He has held a number of visiting and guest professorships at universities around the world.

He was made a Member of the Academia Europaea in 1989 and a Full Member of the Academia Scientiarum et Artium Europaea in 1993. In 2001 he was awarded the Order of Merit of the Federal Republic of Germany.