<p>Parents’ happiness is vital for cultivating young children’s social-emotional competence. However, relatively little is known about the underlying processes through which parents foster children’s functioning. The present study investigated mindful parenting as a mediator for the relations between mothers’ and fathers’ happiness and young children’s social-emotional competence. Specifically, mothers and fathers of 238 first-year kindergarteners in Hong Kong were recruited to complete a set of questionnaires three times at a six-month interval. Cross-lagged path analysis demonstrated that mothers’ mindful parenting mediated the link between their own happiness and children’s social-emotional competence. Although fathers’ mindful parenting did not serve as a mediator, it was consistently related to their own happiness and children’s social-emotional competence over time. Furthermore, actor and partner effects of happiness and mindful parenting were also noted between mothers and fathers. The present findings revealed mother-to-father and father-to-mother effects, but not child-to-parent effects. Despite the bidirectional effects between mothers and fathers, mothers’ happiness is particularly crucial for their practice of mindful parenting. Both mothers’ and fathers’ mindful parenting practice is essential for children’s social-emotional development.</p>