The heat transfer characteristics of a fully confined impingement jet are experimentally and numerically evaluated. Full surface heat transfer coefficient distributions are obtained for the target and impingement plate of the model using the transient liquid crystal technique and a commercial CFD solver. The confined box consists of a single round jet impinging over a flat surface at relatively low jet-to-target plate distances, varied between 0.5 and 1.5 jet diameters. The impingement geometry is blocked from the three sides, and therefore, the air of the jet is forced to exit the model in a single direction resulting in a fully confined configuration. Experiments were carried out over a range of Reynolds varying between 16,500 and 41,800. The experimental data is compared to the numerical simulations aiming to quantify the degree of accuracy to which the heat transfer rates can be predicted.