This study aims to investigate factors affecting the Capital Structure Decisions of listed firms in Egypt and Nigeria. The data collection instrument was the financial statements of Nigerian and Egyptian listed firms, which consisted of an unbalanced panel of 60 firms over 11 years. Only 176 observations for 16 Egyptian firms and 165 observations for 15 Nigerian firms were statistically valid and free of missing data. Panel Data analysis was employed to test the research hypotheses through EViews and SPSS programs. The study results indicated that there were significant effects of financial cost (Market book ratio, stock return, and deflated return) on capital structure decisions (book leverage, long-term capital structure, and Short-term capital structure) of the listed firm in Egypt and Nigeria. This effect was found to be a negative effect for the financial costs (market-to-book ratio and stock return) on book leverage, long-term capital structure, and Short-term capital structure of a listed firm in Egypt and Nigeria and a positive for the market-to-book ratio on both book leverage and the short term capital of listed firms in Nigeria.  Finally, the results showed that there is an insignificant effect of financial costs (deflated return and stock return) on the long-term capital of listed firms in Egypt and Nigeria.