Prior to his current position in Arizona, Hanemann was assistant at London School of Economics (1967-1968), teaching fellow at Harvard University (1970-1975), and between 1976 and 2011 professor of environmental and resource economics in the Department of Agricultural and Resource Economics at the University of California, Berkeley, where he still collaborates.
Previamente á súa posición actual en Arizona, Hanemann foi asistente na London School of Economics (1967-1968), axudante de cátedra na Universidade Harvard (1970-1975) e, entre 1976 e 2011, profesor de economía ambiental e dos recursos no Departamento de Economía Agraria e dos Recursos da Universidade de California, Berkeley, onde aínda colabora.