In this study, the dehydration and degradation kinetics of bioactive compounds of mandarin slices were observed under oven and vacuum drying conditions at 55, 65 and 75C. The dehydration kinetics of the mandarin slices was described by seven thin-layer drying models. The Page model with R-2 of 0.992-0.999 was determined to be the best model. Degradation kinetics of total phenolic content, total flavonoid content, antioxidant capacity and vitamin C content were described using a first-order kinetics model with R-2 of 0.838-0.979. Despite the faster drying, degradation of the total phenolic and flavonoid content increased under vacuum. However, the vitamin C degradation of mandarin slices in oven drying was two times more than in vacuum drying. The antioxidant capacity was protected at the lower temperature for vacuum drying, the opposite of oven drying. In addition, oven drying generally caused more color changes and required more energy.