This study examined the moderator effect of social support on the relationship between stress and depression of university students. A total of 632 undergraduate students completed the measures of perceived stress, perceived social support, and depression. Hierarchical regression analysis showed that social support moderated the association between stress and depression. Undergraduate students with high stress reported higher scores in depression than those with low stress with low social support level. However, the impact of stress on depression was much smaller in the high social support group compared with that in the low social support group.