Previous studies have shown that personal factors serve as mediators in the link between self-compassion and subjective well-being (SWB). However, these studies have neglected the possibility that online prosocial behavior (OPB) may serve as a mediator in the link between self-compassion and SWB. Based on the PERMA theory of well-being and the protective-protective model, the current study examined whether OPB would mediate the association between self-compassion and individual SWB, and whether gratitude would moderate the association between self-compassion and OPB. A valid sample of 1488 college students (M[subscript age] = 19.84; SD = 1.61) filled out questionnaires regarding demographics, self-compassion, OPB, gratitude, and SWB. Results showed that, after controlling for gender, age, daily online time, and social desirability, OPB mediated the association between self-compassion and individual SWB, and gratitude strengthened the positive association between self-compassion and OPB. These findings reveal that high self-compassionate and grateful people can enhance their subjective well-being through behaving prosocially online.