This work assesses the performance of pin-fin heat sinks with confined impingement cooling using numerical simulation. The extent to which the Reynolds number, the height and the width of the fins, the nozzle-to-heat sink distance, the thermal conductivity, the upper confining plate and the fin number affect the thermal resistance are considered. The work shows that increasing the Reynolds number reduces the thermal resistance, but the effect decreases slowly as the Reynolds number increases. Although increasing the fin height can reduce the thermal resistance, reduction decreases. The fin width that is associated with the minimum thermal resistance increases with the Reynolds number. The optimal nozzle-to-heat sink distance increases with the Reynolds number. The thermal resistance decreases with an increasing thermal conductivity; however, the drop in the thermal resistance becomes smaller. The presence of the upper confining plate increases the thermal resistance. Additionally, the thermal resistance initially decreases and then increases slowly as the fin number increases.