Background: We examined effects of trait self-control, constructs from social cognition theories, and intentions on health behaviours. Trait self-control was expected to predict health behaviour indirectly through theory constructs and intentions. Trait self-control was also predicted to moderate the intention–behaviour relationship. Methods: Proposed effects were tested in six datasets for ten health-related behaviours from studies adopting prospective designs. Participants (N = 3,249) completed measures of constructs from social cognition theories and self-control at an initial time point and self-reported their behaviour at follow-up. Results: Results revealed indirect effects of self-control on behaviour through social cognition constructs and intentions for eight behaviours: eating fruit and vegetables, avoiding fast food, dietary restrictions, binge drinking, physical activity, walking, out-of-school physical activity, and pre-drinking. Self-control moderated the intention–behaviour relationship in four behaviours: dietary restriction, and alcohol-related behaviours. Conclusions: Mediation effects suggest that individuals with high self-control are more likely to hold beliefs and intentions to participate in future health behaviour, and more likely to act. Moderation effects indicate that individuals with high self-control are more likely to enact healthy intentions and inhibit unhealthy intentions, but findings were restricted to few behaviours. Training self-control and managing contingencies that derail goal-directed action may be effective intervention strategies.