Little is known about the mediating and moderating mechanisms that underlie the relationship between social support and school engagement. The present study aims to analyse: (1) the mediating role of life satisfaction on the association between social support (from teachers and friends) and school engagement; and (2) the moderating role of school climate in the relationships which exist between social support, life satisfaction and school engagement. Participants were 1397 adolescents (12-16 years old). Analyses were performed using the PROCESSv.4 macro and SPSSv.27. The results reveal that life satisfaction fully mediates the influence of support from friends on school engagement, and partially mediates the predictive effect of support from teachers on that same variable, with the indirect effect of support from teachers being moderated by school climate. The theoretical and practical implications of these results are discussed.