This paper examines the interaction between mutual fund flows and stock returns in Greece. Specifically, we investigate the possibility of a causality mechanism through which mutual funds flows may affect stock returns and vice versa. The statistical evidence derived from the error correction model indicates that there is a bidirectional causality between mutual fund flows and stock returns. Cointegration results show that mutual funds flows cause stock returns to rise or fall. This may be explained by the fact that, in Greece, equity mutual funds are obliged by law to invest a certain percentage of their cash in stocks. Thus, inflows and outflows of cash in equity funds seem to cause higher and lower stock returns in Greek stock market.