How do members of regional parliaments engage in EU policymaking? This paper examines how and why members of the Walloon, Flemish and Brussels regional parliaments vary in their EU-contacting activities, by adapting a German survey. Belgium makes a relevant case, as the ‘in foro interno, in foro externo’ principle entitles regions to conduct foreign policy, including EU affairs in those areas they possess internal competency. Our data show that the level of EU-contacting activities of Belgian regional parliamentarians is overall low, mainly directed towards informational activities and taking place in the direct environment of the parliamentarians. The variation in EU-related activities is best explained by individual-level factors such as the perceived salience of Europe for their own careers, their perceived influence on EU policymaking and their position towards European integration.