Research has demonstrated that family socioeconomic status is an important determinant of people's life satisfaction, in that individuals from disadvantaged backgrounds are typically less satisfied with their life than the rich. But little is known about the mediating and moderating mechanisms underlying this relation. The present study examined the mediation effect of adolescents' self-esteem in the association between socioeconomic status and life satisfaction, and whether this mediating process was moderated by optimism. A sample of 668 Chinese adolescents (mean age = 14.53 years, SD = 1.81) completed anonymous questionnaires regarding SES, life satisfaction, self-esteem and optimism. Multiple regression analyses revealed that the association between SES and life satisfaction was mediated by self-esteem. Moreover, the mediating effect of self-esteem was moderated by optimism, with the mediating effect being stronger for individuals with low optimism than for those with high optimism. These findings can be beneficial to our understanding of how and when SES impacts adolescents' well-being. Moreover, the present study highlighted the importance of using the organism-environment interaction to explore potential protective factors for individuals from disadvantaged backgrounds. A person cannot choose where he comes from (e.g., low socioeconomic status), but can choose whom he wants to be (e.g., optimist).