Based on data from the China Education Panel Survey (CEPS), this study conducted an empirical analysis of the effect of parent educational expectations on the competence development of rural left-behind children and the underlying mediating mechanism. The research findings reveal that rural left-behind children have far less developed competencies than their non-left-behind counterparts and that parent educational expectations significantly and positively influence the competence development of left-behind children. Specifically, parent academic expectations impose the greatest impact on academic results of left-behind children; parent expectations of child education levels have the widest effects on various competencies of left-behind children; Parent involvement and teacher support exert a chain mediating effect on the relationship between parent educational expectations and the competence development of rural left-behind children. The mediation effect of teacher support or the concurrence of teacher support and parent involvement remarkably promoted the competence development of rural left-behind children, while parent involvement alone results in masking effects, which impede the improvement of their competencies to some extent.