--- - |2 Abstract Parents' supportive emotion socialization behaviors promote children's socioemotional competence in early childhood, but the nature of parents' supportiveness may change over time, as children continue to develop their emotion‐related abilities and enter contexts that require more complex and nuanced social skills and greater autonomy. To test whether associations between parents' supportiveness of children's negative emotions and children's socioemotional adjustment vary with child age, 81 parents of 3‐ to 6‐year‐old children completed questionnaires assessing their responses to children's negative emotions and their children's emotion regulation, lability, social competence, and behavioral adjustment. As predicted, child age moderated the associations between parents' supportiveness and children's socioemotional adjustment. For younger children, parents' supportiveness predicted better emotion regulation and less anxiety/internalizing and anger/externalizing problems. However, for older children, these associations were reversed, suggesting that socialization strategies which were supportive for younger children may fail to foster socioemotional competence among 5‐ to 6‐year‐old children. These results suggest the importance of considering emotion socialization as a dynamic, developmental process, and that parents' socialization of children's emotions might need to change in response to children's developing emotional competencies and social demands. - Social Development, Volume 27, Issue 3, Page 466-481, August 2018.