This study evaluates overall monthly performances of 8 Islamic mutual funds (IMFs) in comparison with 24 conventional mutual funds (CMFs) for the period of January 2006 to December 2011 (96 months) divided into pre-financial crisis phase (27 months) and during financial crisis phase (45 months). The study aims at investigating the performance differences, if any, as well as determining factors affecting the performance of mutual funds. It employs Sharpe, Treynor and Jensen ratios as risk-adjusted performance measures. The paper concludes that the performance of IMFs is not significantly different from the CMFs counterparts in the pre-financial crisis phase or during the financial crisis phase. The study concluded that the performance of IMFs is not significantly different from the CMFs counterparts in the pre-financial crisis phase or during the financial crisis phase. Moreover, total risk and systematic risk significantly affect the performance of mutual funds. Income & Growth objective is an important variable that is accompanied with an increase in the performance of the fund. Growth objective and Age also play significant roles in interpreting the performance of mutual funds.