Research Findings: This study examined the contribution of teacher-student conflict at kindergarten to the child’s school adjustment in primary school using a Hong Kong sample. It investigated self-regulation as a mediator and parents’ positive relations with others as a moderator in that transition. At Time 1 (T1), kindergarten teachers reported their levels of conflict with individual children (N = 324, 168 girls), whereas children’s self-regulation was assessed with a Head-Toes-Knees-Shoulders Task. Fathers and mothers also rated their positive relations with others. At Time 2 (T2; 8 months later), when children were enrolled in primary school (N = 247, 126 girls), primary school teachers rated how well they adjusted to the new school. Moderated mediation analyses showed that although the direct effect of T1 teacher-student conflict on T2 school adjustment was not significant, the indirect effect of self-regulation was. T1 teacher-student conflicts were negatively related to children’s self-regulation, which in turn predicted subsequent school adjustment. Interestingly, this indirect effect was significant only when parents’ positive relations with others were low rather than high. Practice or Policy: The findings highlight the importance of both a warm and caring relationship in the home and self-regulation to successful school transition. Copyright © 2018 Taylor & Francis Group, LLC.