Research Findings: This study aims to explore the possible mediators between social support and parenting competence in Chinese mothers of preschoolers. Altogether 538 Chinese mothers were sampled and surveyed with the Social Support Rating Scale (SSRS), Psychological Capital Scale (PCS-24), and the Chinese versions of the Parenting Sense of Competence Scale (C-PSOC). The results indicated that: (1) Chinese mothers' social support, psychological capital, and parenting competence were medium-level, and there were significant differences across different demographical profiles; (2) social support was positively correlated with maternal psychological capital (MPC) (r = 0.454, p < 0.001) and parenting competence (r = 0.288, p < 0.001); while MPC was positively correlated with parenting competence (r = 0.519, p < 0.001); (3) further regression analysis showed that social support significantly predicted MPC ([beta] = 0.456, p < 0.001) and parenting competence ([beta] = 0.280, p < 0.001), while MPC significantly predicted parenting competence ([beta] = 0.543, p < 0.001); (4) MPC significantly mediated the relationship between social support and parenting competence (95% CI =[0.2355,0.3784], F = 112.530, p < 0.001). The educational implications of these findings are also discussed. Policy and Implications: The findings indicated that sufficient support for building up maternal psychological capital should be provided to better implement social support for Chinese mothers and enhance their parenting competence.