The main purpose of the present research is to investigate time variation in the marginal value and marginal rate of Firms’ Cash Holdings in the Tehran Stock Exchange. The study period is between 1388 and 1392 and the statistical sample of the study is 101 companies listed on Tehran Stock Exchange (TSE). We use Panel-Data Regression and EGLS method to estimate the model parameters. The results of this study reveal that marginal value of cash is less than its face value and marginal rate of cash holding is a decreasing rate. Finally, the findings show that marginal value of cash varies over time.