The relations between aspects of social understanding (e.g., theory of mind, ToM, and emotion understanding, EU) were studied in relation to language and effortful control (EC). Data were collected when children were 30, 42, and 54 months of age (N's = 216, 192, and 168 for T1, T2, and T3, respectively). Children were assessed via mother and caregiver reports, and through observational measures. Although language and ToM did not relate within time, there was limited support for early language positively predicting later ToM. Language and EU were positively related within time, and there was some support for early language positively predicting later EU. Unexpectedly, significant positive relations were found for early EU predicting later language. ToM and EC were positively related within T3, and there was some support for early EC predicting later ToM. EU and EC were often positively related within time. Early EU also tended to positively predict later EC, whereas the opposite relation was not found. There was no support for significant a significant relation between EU and ToM. Findings suggest that children's early language may lead to later EC, and that early EU may help promote later EC and language; thus, it is important for parents and teachers to promote these early skills.