Ownership dispersion is an important effective factor in determining bid-ask spread. Bid-ask spread has important role in stock liquidity. Some researches indicate that increasing in ownership dispersion leads to decrease bid-ask spread and therefore increase stock liquidity. No many researches have done about the relationship between ownership dispersion and bid-ask spread in Iran. Therefore the main goal of this paper is to review the relationship between ownership dispersion as an independent variable and bid-ask spread as dependent variable in Tehran Stock Exchange. Therefore 156 firms that their required data for a seventh year period was available were studied. The multivariate pooled regression model is used to examine the hypotheses. The conclusions indicate that there is no significant relationship between ownership dispersion and Bid-Ask Spread in Tehran Stock Exchange.