Social exclusion experiences thwart fundamental human needs, and threaten youths' mental health and wellbeing. Given the literature supporting the protective effect of social support, the present study investigated whether social support mediated and moderated the relation between social exclusion and psychological wellbeing at school. Sample consisted of 407 adolescents (49.9% of female) with ranging in age between 11 and 18 years (M = 13.94, SD = 1.64). Findings of the structural equation modeling analyses indicated that social support sources-family, peer and school- had mediating effect on the relationship of social exclusion and youths' psychological wellbeing. Additionally, regression analyses showed that social support had also a moderator role on this association. However, the role of these resources (family, school and peer support) varied with regard to gender, and herein the effect of social support was greater in female students. Moreover, school support moderated the association of social exclusion and female students' psychological wellbeing, while peer support had a moderator role on this relation for male students. In sum, the study results support that youths who perceive themselves as being socially excluded at school have lower social support and psychological wellbeing, and the importance of social support resources on youths' psychological wellbeing in adolescents. Implications for future research and practice are discussed, and several suggestions are presented.