Based on the data of A share listed subsidiaries in China between 2010 and 2021, this study investigates the impact of parent company over appointment of directors on the investment efficiency of subsidiaries. The findings reveal an inverted U shaped relationship between the parent company’s over appointment of directors and the investment efficiency of the subsidiaries. Further research shows that the governance effect of the parent company’s over appointed directors is more significant in samples characterized by a small board size, high interaction intensity, and low social capital of other subsidiary directors. The over appointment of directors by the parent company influences the investment efficiency of the subsidiaries through supervision effect, resources effect and information communication effect. In terms of heterogeneity analysis, it is discovered that non state owned equity and multiple large shareholders enhance the positive governance role of over appointed directors from parent companies. These conclusions contribute to the existing research on over appointed directors in the field of corporate governance and provide empirical evidence and theoretical implication for enhancing the quality of investment decision making within the parent subsidiary context.