This thesis is regarding the numerical investigation of Blended winglet device. The measure of how it could improve aircraft's performance is based on the observation of lift coefficient, drag coefficient and vortex formation under standard flight cruising conditions. Analyses were conducted using computational fluid dynamics to obtain the best results. Other software such as Pro Engineer was used to aid this investigation. As reference, several other wing and winglet models were generated to be compared to the winglet of interest. Results have shown an overall improvement on the aerodynamic characteristics of wings when equipped with blended winglet. The reason why this investigation is interesting is because not much investigation had been done on Blended winglets. Only few numerical and experimental studies had been done, most were published and owned by Boeing. This study will provide substantial data to benefit the progress of winglet technology.