This study examines the relationship between firm size and tax avoidance in the Egyptian listed companies. To achieve this goal, the study relied on a sample of 88 listed non-financial Egyptian companies, with 473 firm-year observations, between 2013 and 2018. In order to test the hypothesis, the study used three indicators to measure the firm’s size: Total assets at book value, total assets at market value, and total revenues. The study also used the effective tax rate as an inverse measure of the company's tax avoidance level. After controlling the effects of financial leverage, growth opportunities, firm profitability, capital intensity, and inventory intensity on the effective tax rate, the researcher find by using multiple linear regression analysis, a negative relationship between firm size and effective tax rate. This means that there is a positive relationship between firm size and the company's tax avoidance level. This result represents a clear empirical support for the political power hypothesis, and also refutes the expectations of political cost theory regarding the existence of a positive relationship between firm size and the company's tax burden.