Lack of proper corporate governance mechanisms can pave the way for management opportunistic actions one of which is to lead tax avoidance activities towards their own benefits, which in turn may waste tax resources. The purpose of this paper is to investigate the effect of intellectual capital on the relation between corporate governance and tax avoidance of firms listed in Tehran Stock Exchange. The sample consists of 94 firms listed in Tehran Stock Exchange during the period from 2010 to 2015. The data is analyzed through regression model using panel data. The results indicate that intellectual capital does not modify the relation between corporate governance mechanisms and tax avoidance. This means that corporate governance mechanisms affect tax avoidance directly and intellectual capital does not play any role in it. In particular, findings show that strong corporate governance leads to improvement of financial reporting quality and, ultimately, helps the effectiveness of tax planning actions.