This research investigated the relation between individual differences in inhibitory control and emotion regulation. Preschool children (N=53) ages 4-6 (M=5; 0) were assessed on brief batteries of inhibitory control of prepotent responses and emotion regulation. Individual differences in inhibitory control were significantly correlated with children's ability to regulate their emotions. This relation held up even after controlling for age and verbal ability, and persisted for both Emotion Understanding and "online" control of emotional expressions that were negative (Disappointing Gift) or positive (Secret Keeping). Parent report of children's self-control and emotion regulation corroborated the behavioral results. These findings suggest that executive control of attention, action, and emotion are skills that develop in concert in the preschool period. However, there was also evidence of a quadratic relation in which emotion regulation was optimal at intermediate levels of inhibition, highlighting the interplay of both cognitive control and temperament in socio-emotional functioning.