Numerical investigation of the effect of winglets on the blade performance for wind turbine is performed. Winglets with parameters of their height and 90° angle facing upstream (UW configuration) and downstream (DW configuration) direction from blade tip are proposed. Furthermore, the winglet tip thickness is varied to 100%, 85% and 70% of tip blade thickness to investigate its effect. Numerical simulation with RANS equations in combination with k-ω SST turbulence model was performed. Grid convergence index was applied to ensure the grid independence of the solution. Moving reference frame method was used to perform the blade rotating motion. Numerical results for the blades with and without winglet are compared to examine the effect on the blade performance at different flow conditions. Generated torque and thrust are used to evaluate the blade performances. The present numerical results for blades without winglet were found in well agreement with experimental data from NREL phase VI of a horizontal wind turbine. The UW configuration showed improvement on the blade torque, and reducing winglet thickness tends to increase the torque. Also, UW configuration showed it is able to improve the blade tip wake characteristic compare to the normal configuration. While winglet with DW configuration indicated lower blade torque and worse performance compared to the normal configuration.