Objective: Given the role inhibitory control plays in both ADHD and communication, this study examined whether inattentive and hyperactive-impulsive traits mediate the impact of weak inhibitory ability upon the knowledge and application of pragmatic rules early in development. Method: Participants were 36 typically developing preschoolers and their caregivers. ADHD traits were assessed per caregiver report. Inhibition was assessed in children using a distraction task. Pragmatic language was assessed by asking children about hypothetical social situations (knowledge) and by asking caregivers to report on children’s actual communicative behaviors (application). Results: Individual differences in inhibition predicted both facets of pragmatic language development. Hyperactive-impulsive behaviors were a significant mediator of this relationship—but only with regard to children’s ability to effectively apply pragmatic rules in everyday life. Conclusion: Our findings suggest that social communication difficulties in some young children are a downstream consequence of hyperactive-impulsive behaviors that arise from poorly developed inhibitory control.