 He became a professor of the English language, Comparative Literature, Ethnic Studies, American Studies and Cultural Studies in the United States, Europe, the Philippines, and Taiwan.From 1961 to 1963, San Juan was appointed as a fellow and English-language tutor at Harvard University.Among the other universities in the United States where he taught include the University of California at Davis, the University of Connecticut at Storrs, and the Brooklyn College of the City University of New York.