This longitudinal study investigated bidirectional associations between pupils' social competence and their interpersonal relationships and classroom climate in segregated special education schools for pupils with emotional and behavioral disorders in the Netherlands. Participants were in Grade 4 and 5 in School Year 1 (N = 441) and Grade 5 and 6 in School Year 2 (N = 504) (M[subscript age Time1] = 10.82, SD = 0.86). Digital surveys were administered to pupils and teachers twice each school year to gather information about pupils' relationships with teachers and peers, classroom climate (structure, atmosphere), and social competence. Structural path models were estimated separately for each school year. Altogether, classroom structure and peer relations were inconsistently linked with teacher and self-reported social competence. Peer relationships (first school year) and structure (second school year) predicted teacher-reported social competence. Self-reported social competence predicted peer relationships, while teacher-reported social competence predicted structure (second school year). Explanations and implications of the findings are discussed.