Grounded in Basic Psychological Needs Theory (BPNT; Deci and Ryan in Intrinsic motivation and self-determination in human behavior. Plenum, New York, 1985; Psychol Inq 11(4):227–268. doi:10.1207/S15327965PLI1104_01, 2000; Ryan and Deci in Am Psychol 55(1):68–78. doi:10.1037/0003-066X.55.1.68, 2000), the present study mainly aimed to (1) test a theoretically-based model proposing that the satisfaction of three basic psychological needs at school mediates the relationship between school-related social support (i.e., teacher support and classmate support) and school-related subjective well-being and (2) explore the invariance of the model across gender and age groups. A total of 1476 Chinese adolescents (males = 712; early adolescents = 676; Mage = 15.40) completed a multi-measure questionnaire tapping the targeted variables. Structural equation modeling was used to examine the hypotheses. Results indicated that school-related social support (i.e., teacher support and classmate support) related statistically significantly to adolescents’ school-related subjective well-being. Furthermore, a multiple-mediators analysis indicated that autonomy, competence and relatedness needs satisfaction at school partially mediated the relation between teacher support and school-related subjective well-being, and fully mediated the relation between classmate support and school-related subjective well-being. Lastly, the results supported partial invariance of the model with respect to gender and age groups. Limitations of the study are considered and applied considerations to improve adolescents’ school-related subjective well-being are discussed.