Drawing on qualitative case studies of two specific European decision-making processes in the agricultural and environmental sectors, this paper discusses how and why Belgian regional parliaments activated (or not) their control mechanisms to scrutinise their respective regional ministers. The findings show that parliamentary scrutiny of the agricultural and environmental policy fields has undergone a process of institutional and behavioural Europeanisation. Belgian regional parliaments rely mostly on classical parliamentary tools aimed at gathering information and, to a lesser extent, on constraining instruments aimed at influencing their government. Rather than trying to influence the EU negotiations, the MPs try to assess the potential impact of the reforms on their regional policy sectors. The findings also demonstrate that domestic media coverage and political salience of the EU negotiation associated with important implementing powers of regional parliaments have a positive effect on the level of scrutiny conducted by Belgian regional assemblies.