The vast majority of studies on theory of mind (ToM) have focused on the preschool years. Extending the developmental scope of ToM research presents opportunities to both reassess theoretical accounts of ToM and test its predictive utility. The twin aims of this longitudinal study were to examine developmental relations between ToM, executive function (EF), and teacher-rated social competence in middle childhood. One hundred thirty-seven children (69 males) were followed across a 4-year period spanning middle childhood (M ages at Waves 1 and 2 = 6.05, SD = 0.35, and 10.81, SD = 0.35, respectively). Individual differences in ToM were moderately stable across middle childhood. Although there were concurrent associations between ToM and EF at both time points, there were no longitudinal links between these constructs. In contrast, there were concurrent and longitudinal links between ToM and teacher-rated social competence, such that individual differences in ToM predicted later social competence at school. These results are discussed in light of competing theories about the links between ToM and EF and the importance of individual differences in ToM for children's social lives.