This paper analyzes the impact of pension fund investment management on stock markets using a robust panel threshold model (ROPTM) which combines a panel threshold model with a robust regression model. We use panel data for some OECD countries and Taiwan to test the validity of our proposition s. The data is divided into low and high investment regions based on the value of stocks as a percentage of total financial assets of the pension fund. In the high investment region, pension funds have a positive impact on stock markets. Whereas, in the low investment region, the positive impact seems to disappear.