This study examined both the mediating and moderating effects of global self-esteem on the relationship between social support and subjective well-being among Chinese university students. Three hundred and ninety-one university students (260 males and 131 females) from two different Chinese universities completed the social support scale, the self-esteem scale and the subjective well-being scale. Hierarchical regression analysis showed that global self-esteem partially mediated the influence of social support on life satisfaction and positive affect, whereas it fully mediated the influence of social support on negative affect. Moreover, global self-esteem moderated the relationship between social support and life satisfaction, and positive affect, but not negative affect. When students reported a high level of global self-esteem, those with high social support reported higher scores in life satisfaction and positive affect than those with low social support. However, there were no differences in life satisfaction or positive affect between groups with high and low social support when global self-esteem was low. The significance and limitations of the results are discussed.