Abstarct: The aim of present study is to examine the effect of firm’s fundamentals and macroeconomics on idiosyncratic return volatility. In this regard, 136 companies using systematic elimination method is selected as the sample of the research from companies listed in Tehran Stock Exchange (TSE) for the period of 2007 to 2023. Fundamental idiosyncratic volatility (FUND), as the main independent variable, is calculated baxsed on Irvin & Pontiff's method, while idiosyncratic return volatility (IVOL) as the dependent variable is obtained baxsed on three-factor Fama-French and Campbell models. Multiple linear regression estimation is used to examine the effect of firm's fundamentals and macroeconomics on idiosyncratic return. Thanks to another estimation model the role of institutional shareholders as an intervening variable on the relation between firm’s fundamentals and idiosyncratic return volatility was examined. The result shows that FUND has a significant effect on IVOL calculated by both Fama-French and Campbell model.