The 2009-2018 period witnessed many political and economic changes in the world and the Arab Gulf in general, and in the Kingdom of Saudi Arabia in particular. These changes may affect the performance of the banking sector and threaten the growth and continuity of banks. This study examines the performance of Islamic and conventional banks in this period in the Kingdom of Saudi Arabia. The study sample includes all the twelve Saudi national banks (8 conventional banks and 4 Islamic banks). The study relies on the indicators of liquidity, profitability, activity, and financial solvency. The differences between the means of the financial ratios of conventional banks and Islamic banks will be measured using descriptive and inferential analysis. Data analysis will be carried out using the Statistical Analysis Program (SPSS). The findings have shown that Islamic banks have high liquidity compared to conventional banks. Profitability indicators showed that there are no differences between conventional banks and Islamic banks on the use of their own resources to achieve profits in the average of study period. In addition, the activity indicators showed that the conventional banks employ their resources better than Islamic banks, while both types of banks are approximately similar in investment-deposit ratio. Moreover, both conventional banks and Islamic banks has an acceptable solvency. The study is concluded with a set of recommendations including that Islamic bank must beware that the liquidity does not reach the level of excess liquidity. Islamic banks must work towards increasing cooperation, coordination, and integration between banks at the local and international levels, as well as develop an Islamic financial market and innovate Islamic financial tools. In addition, it is recommended for Islamic banks to amalgamate to form an ideal size of an Islamic bank to be a role model.