This cross-sectional study relied on circumscribed measures of emotion regulation and dysregulation to examine their role in mediating the associations of maternal responsiveness and effortful control with social competency and externalizing symptoms. We examined those associations in an understudied cultural context, Turkey, with 118 preschoolers. Emotion regulation and dysregulation showed differential associations with broad indices of self-regulation such that emotion dysregulation predicted both low social competency and high externalizing symptoms but emotion regulation was only associated with high social competency. Effortful control was unrelated to emotion regulation but was associated with lower levels of emotion dysregulation. Effortful control had both direct and mediated associations with externalizing and social competency (mediated by lower emotion dysregulation). Findings also showed that maternal responsiveness was associated with better social competency and lower externalizing. Those associations were both singly (through effortful control) and doubly mediated (through effortful control and lower emotion dysregulation), similar to US samples. The study contributes to a better understanding of the factors and mechanisms that speak to children's self-regulation.