A simulation-based study is carried out on a counter-flow minichannel heat exchangers with smooth and staggered pin-fins. The heat exchangers consist of two layers of hot and cold fluids. Each layer contained 10 minichannels with width of 2 mm and length of 100 mm; the height of the minichannel is 2 mm and the spacing between each minichannel is 0.5 mm. The heat exchanger is studied with water-water fluids. The investigation is carried out for different Reynolds numbers between 150 and 2000. The effectiveness is determined using the inlet and outlet temperatures of the fluids. Based on the investigation, it is observed that increasing Reynolds number decreases the effectiveness, and increases the overall heat transfer coefficient. It is also observed increasing Reynolds number decreases the friction factor. It was clearly observed that the heat transfer rate is higher for pin-fin minichannel compared to smooth channel. It is also noted that overall friction factor in pin-fin minichannel is higher than that in smooth channel.