Cooling performance was determined on a film cooled surface with staggered array jet impingement cooling at various Biot numbers. Heat transfer experiments were conducted using infra-red thermography. Conjugated heat transfer was analyzed with the combined effects of conduction through the test plates and convective heat transfer due to the arrayed jet impingement. The angle of the film cooling holes was 35° and that of the jet impingement holes was 90°. The film and jet impingement holes on each plate were arranged in staggered patterns, and the film cooling holes and jet impingement holes were also positioned in a staggered pattern. The distance between jet and film hole plates was fixed. When jet impingement was added to the internal cooling, the averaged total cooling effectiveness was enhanced. At low Biot numbers, meaning that cooling performance dominated over the conduction effect, the temperature distribution became more uniform due to higher conductive heat transfer. The total cooling effectiveness was strongly related to the Biot number of the plate, and comparing the existing 1-D conduction analysis with the experimental results to predict the total cooling effectiveness in an actual gas turbine engine.