A modified shuffled frog leaping algorithm (SFLA) and cooperative spectrum sensing for cognitive radios based on the modified SFLA are proposed. Simulations are performed to compare the performance of the modified SFLA and traditional SFLA. The performance of the proposed cooperative spectrum sensing method based on the modified SFLA and that of the cooperative spectrum sensing method using modified deflection coefficient (MDC) are also compared. Results show that the proposed SFLA outperforms the traditional SFLA, and the proposed cooperative spectrum sensing method based on the modified SFLA gives higher detection probability than the MDC-based method, which validates the effectiveness of the modified SFLA-based cooperative sensing method.