Abstract: This study investigated the influence of corporate governance mechanisms on firm performance of public listed companies in Iraq. Specifically, the study examined the effect of internal audit function, government share ownership and private share ownership on firm performance. The study utilized data extracted from the annual report of public listed companies on the Iraqi Stock Exchange between the period of 2012-2015. The result obtained from the regression revealed a positive and significant relationship between internal audit department establishments, government share ownership and firm performance while it was found that private shareholding does not have any relationship with firm performance. This implies that listed companies that established internal audit department and whose shares are substantially held by the government perform very well due to strong monitoring mechanism. The findings of this study create a case for both policy makers and management of listed companies in Iraq on the significant of sound corporate governance.