The Oscillating Water Column (OWC) wave energy converter with impulse turbine is widely used for wave energy conversion because of its wide operating range. To improve the starting characteristics and conversion efficiency of the turbine, several studies have been conducted. This paper investigates the effect of blade shape numerically on the performance of the turbine under steady flow conditions using Ansys CFX V 14.5. A constant chord length is used and the thickness of the blade is increased with radius from hub to tip. The main objective is to minimize the flow separation on the suction side of the blade near the trailing edge. The results are validated with the experimental results available in the literature. The performance of blades with various thickness has been compared with that of the original blade. It was found that the blade thickness influences the turbine performance considerably. © 2016 Taylor & Francis Group, London.