This mixed-method study examines students' expectations and concerns before transitioning from primary to lower secondary school and the role of students' school-related wellbeing and self-esteem in their concerns. Students reported their beliefs about the forthcoming school transition and filled in a questionnaire assessing school burnout and self-esteem. The results showed that the students had positive expectations comprising comfort, friendships, learning, school environment, increased freedom and teacher -student relations. The students' concerns were mainly related to friendships. Furthermore, results indicated that students who reported concerns about peer relations were likely to experience more exhaustion from school than students who did not report concerns about peer relations. Among girls, concerns about peer relations were also related to a cynical attitude towards schoolwork. This study promotes to understand how students can be prepared and what topics should be specifically discussed with them to support their successful transition from primary to lower secondary school.