Multilevel inverters (MLIs) are getting popular in high power application due to its inherent characteristics of minimal switching losses due to low switching frequency. There are various techniques available for reduction of harmonics. However, minimizing the total harmonic distortion in multilevel inverters as well as the elimination of selected harmonic order using conventional methods do not yield promising results. Therefore, authors have adopted optimization based approach for elimination of 5th, 7th and 11th order harmonics of 9 level inverter. A novel Sine cosine optimization technique has introduced in this work. Further, Newton Raphson method and Sine-Cosine algorithm is compared. According to simulation results, it has been found that the proposed technique yields significantly better selected harmonics reduction with low THD.