In this paper a new method has been proposed to select optimal switching angles based on Firefly algorithm. The resultant equations for the computation of output voltage total harmonic distortion (THD) of a multilevel inverter are used as the objective function. This objective function is used to minimize the THD in the output voltage of a multilevel inverter. While minimizing the objective function, the selective harmonics such as the 5th, 7th, 11th and 13th can be controlled by using the Firefly algorithm. The simulations are performed for an 11 level cascaded multilevel inverter with equal and nonequal dc sources to show the validity of the proposed method. The results show that the proposed firefly algorithm can eliminate selective harmonics in the output voltage of a multilevel inverter. © 2014 IEEE.