This article deals with the exergy analysis of a single layer drying process of mint leaves in a ground source heat pump tray dryer, which was designed and constructed in the Solar Energy Institute, Ege University, Izmir, Turkey. The drying process was realized at three various drying air temperatures of 40, 45 and 50C, and mass flow rate from 0.01 to 0.05 kg/s at a constant relative humidity of 16%. The effects of temperatures and mass flow rates on the exergy losses, exergy efficiencies and improvement potentials of the drying process were investigated. Maximum exergy efficiency of the drying chamber was obtained at a temperature of 50C and a drying air mass flow rate of 0.05 kg/s. The exergy efficiency values were obtained to vary from 76.03 to 97.24% at drying air temperatures of 40-50C with drying air mass flow rates of 0.01-0.05 kg/s.