This research aims to examine how the Board of Director's characteristics (Board Duality, Board Independence and Board Size) and financial performance of the firm affect its capital structure using tax aggressiveness as a moderating variable. To the firm and the shareholders, taxes normally considered as an additional cost as it reduces the available cash flow, that's why firm's tends to apply different tax aggressiveness techniques in strategic tax planning to decrease tax liability and legitimate saving of taxes. The sample used is 58 Egyptian listed companies during the period 2015-2019. This research runs five multiple regression models to examine the relationships between research variables. The statistical results indicate that CEOD and board independence have a positive significant impact on company' capital structure, while board size have a significant negative relationship with capital structure. Moreover, results shows that ROA, current ratio and asset turn over have a negative significant impact on company' capital structure, while ROE have a significant positive relationship with capital structure. In addition, findings show that CEOD and firm size have a positive significant impact on company' tax aggressiveness, while board independence has a significant negative relationship with tax aggressiveness.