Improving heat transfer rate and reducing manufacturing costs are two significant objectives in the optimal design of heat sinks, which are used in electrical devices. Due to economic reasons in cooling applications, different methods were used to increase the efficiency of thermal devices such as creating perforations in fins, which reduces the volume of fins and increases thermal dissipation. In this study, an attempt was made to improve the thermal and hydraulic performance of fluid flow over a three-dimensional array of rectangular perforated fins with different perforations shapes and sizes. Finite volume method with the SIMPLE algorithm was applied to solve the incompressible laminar Navier-Stokes and energy equations. Flow and heat transfer characteristics were presented for Reynolds number (based on fin thickness) from 100 to 350 and a Prandtl number of 0.71 (air). In this study, the effects of perforation size and shape on the average Nusselt number, total drag force, and perforated fin effectiveness were assessed. The results of this investigation confirmed that for a constant heat transfer surface area, the highest values of perforated fin effectiveness and average Nusselt number are obtained for fins with circular perforations.