The present research is concerned with exploring the relationship between tax avoidance and timeliness of earnings announcement. To do so, book-tax difference and effective tax rate are used to measure tax avoidance. A sample of 107 firms listed in Tehran Stock Exchange during the years 2010-2014 were chosen, and the research hypothesis is tested using multivariate regression model based on panel data technique. The results indicate that tax avoidance activities can delay earnings announcement. Having tried to fill the gaps in the related literature, this study help tax authorities, investors and other stakeholders make informed decisions.