This study presents a methodology first built up for the aerodynamic shape optimization for wind turbine rotors and its modified version for a helicopter rotor in hover. The Genetic Algorithm (GA) coupled with an in-house Blade Element Momentum (BEM) tool is used in the design optimization process. The wind turbine blade optimization studies are performed for maximizing the power production at a given wind speed, rotor speed and rotor diameter, while for the helicopter blade optimization in hover, figure of merit is considered. The airfoil profiles along the span are defined by high order Bezier curves, and the control points of the curves are taken as the design variables. The chord length distribution and the twist distribution are also defined by Bezier splines. The sectional aerodynamic loads needed by the BEM method are obtained by using the potential flow solver with a boundary layer model, XFOIL. The BEM calculations for each individual in the GA population may be computed in parallel using OpenMPl. The BEM tool developed is validated with the available wind turbine and helicopter blade aerodynamic data and then design optimization studies are successfully performed. © 2014 by the American Helicopter Society International, Inc. All rights reserved.