De Haan started his academic career in 1966 as researcher probability and statistics at the Mathematisch Centrum, Amsterdam. In the year 1971-72 he was Visiting Assistant Professor at Stanford University. In 1977 he was appointed Professor of Probability and Mathematical Statistics at the Erasmus Universiteit, where he stayed until his retirement in 1998. From 1990 to 1992 he was Associate Dean of the School of Economics. From 2008 to 2011 he was part-time Professor of Statistics at the University of Tilburg.