Mark M.A.C. van Ostaijen is as Associate Professor affiliated to the Department of Public Administration and Sociology (DPAS/ ESSB) at Erasmus University Rotterdam. He works as Managing Director of the LDE Centre Governance of Migration and Diversity. He is a VIDI grant recipient (2025) to conduct international comparative research on the decision-making of ‘street-level workers’ in superdiverse European cities.

In his previous research project at Tilburg University, he conducted etnographic fieldwork on how 'smart urban intermediaries' make a difference in neighborhoods of Amsterdam, Glasgow, Birmingham and Copenhagen. His PhD dissertation 'Worlds between words', was awarded as ‘Best PhD thesis’ by the Erasmus Graduate School. During his PhD research he was one of the founders and chairman of the IMISCOE PhD network, an Organizing Committee Member of the Interpretive Policy Analysis (IPA) conference in Leicester (UK) and a visiting doctoral research fellow at De Montfort University (UK).

He published a Dutch book ‘Wij zijn ons. Een kleine sociologie van grote denkers’ (3th edition), is Committee Member of the Colloquium Critical and Interpretive Public Administration at the Netherlands Institute of Government (NIG), editor of Beleid & Maatschappij and columnist for De Volkskrant.