Heat exchangers with microchannel/mini-channel configurations have wide applications including aerospace, airconditioning, process/power industries, gas turbine cooling, etc. Heat sinks are effective due to the main feature of having fins, however, there are limitations with respect to their applications. The main objective of this study is to observe the changes in the performance of the heat exchanger by calculating effectiveness with respect to Reynolds number, pin fins (two types: Circular and square), and operating conditions. The current study is conducted through Computational Fluid Dynamics (CFD) analysis using ANSYS Fluent solver platform. The CFD geometric model consisted of a top channel with hot fluid (air), the bottom channel (water), and the middle part, aluminum block. Overall, it is noted that the heat transfer is enhanced by adding pin fins along the mini-channel of the heat exchanger. The findings indicated that square fins perform slightly better than circular fins.