The energy demand in Malaysia has shown a drastic increase over the years. The primary energy supply is natural gas, coal, and coke energy extraction. However, these energy extractions are considered unclean and not sustainable. Therefore, renewable energy could be the immediate solution. Furthermore, previous studies in ocean engineering indicated that Malaysia’s sea condition is favorable to be utilized. Overtopping wave energy converters are primarily used for high mechanical to electrical conversion efficiencies. The current study optimizes the turbine for overtopping wave energy conversion devices through computational fluid dynamics simulation software, ANSYS. Findings indicate that the larger the turbine blade diameter, the higher the torque acting on the turbine. This is because the water pressure impact on the linear blade surface is more significant when the diameter of the blade is prominent, resulting in higher torque acting on the turbine. Unlike the diameter of the turbine blade, the number of the turbine blade is not directly proportional to the torque acting on the turbine. Turbine models with four blades illustrate a higher torque value than three and five blades turbines. The highest turbine performance efficiency for straight flow casing is 62.87% with 3091.30W, while spiral casing turbine exhibited outstanding performance efficiency of 94.44% with 4643.82W under the same power input condition. This study calls for future study in the system design optimization of overtopping wave energy conversion technology, such as ocean wave conditions, power take-off systems design, and location selection.