Motor competence and self-regulation develop rapidly in early childhood; emerging work suggests motor competence interventions as a promising way to promote self-regulation (e.g., behavioral inhibition; cognitive flexibility) in young children. We tested the impact of a mastery-focused motor competence intervention (Children's Health Activity Motor Program [CHAMP]) on behavioral and cognitive aspects of self-regulation among children attending Head Start. Grounded in Achievement Goal Theory, CHAMP encourages children's autonomy to navigate a mastery-oriented motor skill learning environment. Children (M age = 53.4 months, SD = 3.2) were cluster-randomized by classroom (6 per condition) to an intervention (n = 67) or control condition (n = 45). Behavioral self-regulation skills were assessed using the Head-Toes-Knees-Shoulders task (HTKS). Cognitive self-regulation skills were assessed using working memory and dimensional card-sorting executive function tasks. Random-effects hurdle models accounting for zero-inflated distributions indicated that children receiving CHAMP, versus not, were almost 3 times more likely to have non-zero HTKS scores at post-test; OR: 2.98 (CI 1.53, 5.81); however, there were no effects on any cognitive aspects of self-regulation (all p's > 0.05). Mastery climate motor competence interventions are an ecologically valid strategy that may have a greater impact on preschoolers' behavioral than cognitive aspects of self-regulation.