Studies have documented that self-esteem and social support mediate the relationship between extroversion and happiness. Most of the studies, however, were conducted in a piecemeal fashion and have rarely evaluated the two mediators simultaneously. It is not clear whether the two mediating effects are equally important or one is greater than the other. Moreover, little attention has been given to the indirect effect of extraversion on happiness through self-esteem then social support (i.e., serial mediating effect). The present study attempts to bridge these gaps by proposing and testing a path model illustrating the mediating effects of self-esteem and social support on the linkage of extraversion and happiness. Undergraduate students (N = 311) completed measures of extroversion, social support, self-esteem, and happiness. Results showed that extraversion, self-esteem, and social support were significantly associated with happiness. As predicted, both self-esteem and social support mediated the relationship between extraversion and happiness, respectively. Results also supported the hypothesized serial mediating effect. In other words, extroverts tend to have high self-esteem which increases supports they receive from friends and family. The high social support, in turn, enhances happiness. Additionally, comparisons among the three indirect effects indicated that the effect of self-esteem was significantly greater than the other two effects. The findings not only shed light on the independent and accumulative mediating effects of self-esteem and social support, but also provide new insight into the difference in strength of the indirect effects.