Purpose: This paper aims at investigating ownership concentration and explore the nature of the relationship between ownership concentration and firms' performance in the Egyptian economy over 2014 -2018. Design /methodology / approach: The required data are gathered from the annual financial statements of the interested companies. The primary sources that have been used to collect data are: The Egyptian Stock Exchange and the Co face Financial Yearbook over the period 2014-2018. The sample of the existing research includes the companies listed in EGX30 over the period 2014-2018.  The researcher employs Ordinary least Square method (OLS) to estimate the impact of ownership structure on firms' performance measured ROA and ROE. Two regression models were employed in this research.  Findings:  My results confirmed that the mean value of ownership concentration of the largest shareholder in this research sample is 18.3570%. This implies that largest shareholder in Egypt has a fairly ownership concentration. Additionally, ownership concentration owned by the largest shareholder in my sample ranges from 17% to 20%. More than half of the total percentage of shares is already in the largest five shareholders' hands. It also suggests that the largest five shareholders have a widely concentrated structure of ownership. Additionally, the ownership concentration by largest five shareholders ranges from 58% to 59%. Ownership concentration measured by shares owned by largest owner contributes positively in enhancing firm's financial performance measured by ROA. However, it decreases significantly returns on equity (ROE). In regards to ownership concentration measured by the percentage of shares owned by the largest five owners, conclusions revealed that this percentage increases significantly the measurements of profitability employed by current research (ROA, ROE).        Originality/ value: This article is one of the first to investigate whether ownership concentration explains the association between ownership concentration and firms' performance.