This study aimed to examine the effects of rater, age and gender on the relationship between theory of mind (ToM) and preschoolers' social competence with peers (SCP). A sample of 152 Chinese urban children aged 4 to 6 years (78 boys and 74 girls) were given ToM scale. Their SCP was measured by teacher report and parent report. There were three main findings: (1) teachers rated children's SCP higher than parents; (2) teacher ratings of SCP were more closely associated with children's ToM than parent ratings after controlling for age and gender; (3) the significant associations between ToM and SCP from cross-informant ratings were only found in the boys and the younger subsamples (aged 4) rather than all preschoolers. These divergent associations indicated that the effective intervention, would require individual and varying ToM training to improve children's SCP.