During the past few years, there have been growing interests among researchers to study the effect of block share ownership on corporate earning especially in developing countries. The purpose of this paper is to consider the impact of block ownership on performance of firms in terms of profitability. The proposed study develops two econometric models and applies them on selected firms from Tehran Stock Exchange over the period 2002-2010. The primary objective of this survey is to find the relationship between return of assets and Tobin & apos; s Q as dependent variables with eight independent variables including company size, sales growth, block ownership, debt and liability ratios, etc. The results of implementation of ordinary least squares on two econometric models reveal that while there is no meaningful relationship between return of asset and block ownership there is a meaningful relationship between block ownership and Tobin & apos; s Q.