Situated within a positive psychology perspective, the current study examined the relations among academic achievement, self-esteem, and subjective well-being (SWB) in school among Chinese elementary school students using a longitudinal mediation model. A total of 807 elementary school students (M[subscript age] = 9.43 years; 52.9% male) completed a multimeasure questionnaire that tapped the targeted variables at 3 time points, across 18 months. After controlling for gender, age, and family socioeconomic status, the results revealed that (a) academic achievement positively predicted later SWB in school; (b) self-esteem at Time 2 completely mediated the relation between academic achievement at Time 1 and SWB in school at Time 3; and (c) significant bidirectional relations were observed between self-esteem and SWB in school. Limitations and practical applications related to the cultural context of China were discussed.