This paper investigates empirically the effect of ownership structure (concentration and mix) on the performance of a sample of 53 Islamic banks across 15 countries during 2005-2009. Regression analyses are conducted to evaluate the impact of the identity of the first shareholders (family, state, institutional) and the degree of concentration on Islamic Banks performance. Our results suggest that ownership concentrated at 49 % and that in 41 banks from the full sample, the ultimate owner‟s is institutional. State investors come in second place as ultimate owners followed by Family ultimate shareholders. Using return on assets (ROA) and return on equity (ROE) as performance measures, empirical evidence shows that there is no obvious correlation between ownership concentration and Islamic bank performance. In addition our results suggest that family and state ownership affect positively bank‟s performance. They indicate also that banks with institutional and foreign shareholders are not performing better either. The empirical findings suggest that the recent global financial crisis exerts a negative effect on of the performance Islamic banks. This work is the first of its kind for Islamic banks. It extends previous research by examining whether or not ownership structure (concentration and mix) affect performance. It also helped to fill the gap in the literature by providing the empirical evidence on large sample involving data relative to 15 countries. It‟s worth noting that collecting manually data on ownership structure (concentration and mix) constitute a large part of the research for this paper.