Since 1998 Jos Vaessen has been involved in evaluation research activities, first as an academic and consultant to bilateral and multilateral development organizations and from 2011 to 2015 as an evaluation manager at UNESCO. Jos firmly believes in a strong link between research and practice. His ongoing involvement in some evaluation-related research and teaching activities as honorary lecturer at Maastricht University contributes to the necessary cross-fertilization between these two domains.

Jos has been author of several internationally peer-reviewed publications, including three books. Notable examples of his publications are: Impact evaluations and development – NONIE guidance on impact evaluation (2009, with Frans Leeuw; NONIE/World Bank), Mind the gap: perspectives on policy evaluation and the social sciences (2009, with Frans Leeuw; Transaction Publishers). His most recent book is: Dealing with complexity in development evaluation: a practical approach (2015, with Michael Bamberger and Estelle Raimondo; SAGE Publications). Jos regularly serves on reference groups of evaluations for different institutions and is a member of the Board of the European Evaluation Society.