Purpose -This study examines the effect of ex-day of cash dividend on stock returns using data of 2.266 cash dividends of 422 listed companies from Borsa Istanbul for the period 1997-2018. Methodology -The event study analysis applied for the event windows opened from the t-30 to t+30, and the market-adjusted model was used to calculate abnormal returns. Findings-It is found that there are positive abnormal returns before ex-day, as prices significantly start to rise at least 22 days before cash dividend ex-day and reach to the its' highest level on the ex-day and then decrease in the following days. Conclusion-Based on our findings, it is found that price anomaly caused by ex-day of cash dividend can be used as a two-step mutually exclusive investment strategy. In the first step, buying firms' shares which are decided to distribute dividend per share more than %100, twelve days before ex-day and selling them at the end of ex-dividend day provides on average 2.96% abnormal return addition to cash dividend over the 13 days, in the second step, short selling the same stocks at the end of ex-day and buying back them on seven days after ex-dividend day provides on average 1.51% abnormal return over 7 days. Using these investment strategies, it is possible to get 4.47% return over market index return in addition to 100% cash dividend per share over the period of 20 days by utilising ex-dividend day anomaly.