This article explores why national judges remain passive on EU legal integration by examining judges’ reasons for not requesting preliminary rulings from the European Court of Justice (ECJ). The article combines insights from social psychology and literature on the role of national courts in European integration to formulate expectations regarding what type of motives guide national judges’ behaviours. Drawing on interviews held with Croatian, Slovenian and Swedish judges, our results reveal three shared reasons judges remain passive: referrals are not required by the formal rules (procedural normative motivation), referrals are not made to protect the parties to the case (substantive normative motivation) and referrals are not made to protect judges’ reputations (instrumental motivation). In addition, we unveil motives that are shared by only judges from one or two Member States, such as not referring cases to uphold the capacity of the preliminary ruling procedure (Swedish judges) and not referring cases due to a fear of sanctions and a lack of knowledge and resources (Croatian and Slovenian judges). We discuss these similarities and divergences in light of the theoretical discussion on the role of courts as active or passive actors in EU legal integration.