Once he obtained his doctorate, Nemoianu taught at the Universities of Cambridge and London (1973–1974), California at Berkeley (1975–1978), Cincinnati (1978–1979), and The Catholic University of America in Washington, D.C. (1979-2016), as well as, in a visiting capacity, at the University of Amsterdam (spring 1995). At the Catholic University of America he has been, successively, associate professor (1979–1985), ordinary professor (1985–1993), and William J. Byron Distinguished Professor of Literature and Ordinary Professor of Philosophy (since 1993). There, he also held the positions of Director of the Comparative Literature Program (1979–1994) and Associate Academic Vice-President for Graduate Studies (1989–1991).