Background <p>This study examines the associations between multiple dimensions of media use, including screen time, parental joint media engagement, rule-setting and preschool children’s prosocial behavior in Singapore.</p> Methods <p>Data were drawn from two waves of a nationally representative study— Singapore Longitudinal Early Development Study, with children’s time diaries being used to enhance the accuracy of media exposure measurement. We employed Structural Equation Modeling and applied propensity weighting to adjust for the selection bias related to screen time and parental joint media engagement at the baseline.</p> Results <p>We found that a sizable preschool children spent long hours on screens, often without parental engagement. We observed a direct positive association between parental joint media engagement and children’s prosocial behavior in Wave 1, which further correlates with the children’s prosocial behavior in Wave 2. No direct associations were found between screen time or rule-setting and young children’s prosocial behavior at either wave, suggesting that active parental mediation through direct parental joint media engagement in preschool children’s media use is more important than the duration of screen use and restrictive rule-setting in supporting children’s prosocial behavior.</p> Conclusions <p>Parental joint media engagement plays a more important role than screen time and rule-setting in affecting children’s prosocial behaviour in early childhood. Our study reveals the need for policies to go beyond focusing solely on quantity of screen time as intervention to emphasize the multidimensional context of media use, especially parental engagement, in order to effectively benefit children’s development.</p>