Little is known about the moderation effect of social support on youth’s civic engagement and meaning in life. To address this research gap, the current study examines the relationship among civic engagement, different sources of social support (family, significant others, and friends), and sense of meaningfulness in life. 1330 High school students in Hong Kong were recruited to participate into a survey in this study. Hierarchical regression analysis was used to examine the possible moderation effect of social support on youth’s civic engagement and meaning in life. The results indicate a positive association between civic engagement and the sense of meaningfulness in life. Social support from family and significant others is also found to be associated positively with the sense of meaningfulness in life. Surprisingly, a negative moderation effect of social support from friends is found in the relationship between civic engagement and the sense of meaningfulness in life, which reminds us to reconsider the nature of friendship support. The results suggest that the government and social workers should continue to facilitate youth participation in civic engagement. Further, more focus should be put on nurturing positive family relationships and support from significant others, from which youth’s sense of meaningfulness can be enhanced.