Cultural contexts influence the development of self-regulation. However, cross-cultural variations and consistencies in different aspects of self-regulation and their academic outcomes within the Asian context are less clear. This study investigated (1) the extent to which the development of hot and cool Executive Function (EF) might differ among children from different cultural backgrounds in a multicultural Asian society, and (2) whether and how the predictive power of hot and cool EF on academic skills might vary across subcultures within the nation. Longitudinal data were collected over two waves from a national probability sample of 2,527 young children in Singapore, consisting of ethnic Chinese, Malays, and Indians. Working memory (WM), Delay of Gratification (DoG), and parent-reported self-control were measured during their preschool years (3-6 years of age) in Wave 1. Reading and mathematical skills were assessed approximately 2 years later in Wave 2. Results demonstrated that ethnic Chinese children typically delayed gratification at age 4, whereas Malay and Indian children only started to delay gratification at age 6. Chinese children also outperformed their Malay and Indian counterparts in WM tasks and standardized achievement tests in reading and mathematics. Parent-reported child self-control did not differ by ethnicity. Across subcultures in Singapore, WM was a robust predictor of reading and mathematical skills and explained the longitudinal relations of DoG to academic skills. Our findings suggest that the developmental gaps in EF during early childhood can contribute to later gaps in academic achievement among ethnic groups. Nurturing self-regulation during the preschool years is essential for promoting children's school readiness.