Behaving in a socially competent manner is a complex process that requires the coordination of a number of cognitive skills. The present study examined the unique contributions of executive functions (i.e., inhibitory control and cognitive flexibility), theory of mind, and verbal skills to socially competent behaviours during social interactions. Children (5- to 8 years old; N = 114) completed an interactive task in both a cooperative and competitive social context, as well as cognitive tasks. There was strong reciprocity in cooperative and neutral, but not competitive, behaviours between partners. Dyadic analysis was used to account for the mutual influence occurring between social actors. Children with more proficient inhibitory control showed less competitive behaviours during the cooperative context, even when controlling for their own and their partners' cognitive skills. Children's executive functioning did not relate to behaviour within the competitive context. Implications for interventions focussed on improving children's social skills are discussed. (Contains 4 tables and 3 figures.)