Sectional aerodynamic design optimization was performed to enhance the aerodynamic performance of horizontal axis wind turbine rotor blades based on a computational fluid dynamics technique. The proposed sectional optimization framework consists of airfoil section contour modeling by the PARSEC shape function and a modified feasible direction search algorithm. To enhance the aerodynamic performance of wind turbine rotor blades, the objective of the design framework was set to maximize the lift-over-drag ratio for each design section. A two-dimensional Navier-Stokes flow solver coupled with a transition turbulence model was used to evaluate the aerodynamic performance during the iterative design optimization procedure. The sectional flow conditions were extracted from the flow of a three-dimensional rotor blade configuration. The design framework was applied to the National Renewable Energy Laboratory Phase VI rotor blade. The design optimization was conducted at nine spanwise sections of the rotor blade. To validate the present methodology, the aerodynamic performances of the original baseline rotor and the rotor after the design optimization were compared by using a threedimensional Navier-Stokes flow solver. It was found that approximately 11% of torque enhancement was achieved after the aerodynamic shape design optimization.