Teachers have a key role in promoting Critical Thinking (CT). However, research on appropriate teaching methods for developing CT is scarce in primary education. This study investigated how CT can be fostered among pupils based on teachers' perceptions of the characteristics that promote CT and create obstacles in primary schools. We interviewed 21 schoolteachers, from 14 EU nationalities, in three European Schools in Brussels (Belgium). The results provide insights on inquiry teaching approach, flexible and structured learning space, a mutual trust relationship in the classroom environment. This research contributes to inform stakeholders on effective CT teaching methods in primary education.