We have studied the antioxidant activity and analyzed active substances of the aqueous and methanol extracts of endemic species Thecocarpus carvifolius Hedge and Lamond. The antioxidant activity was identified and assessed using the DPPH, FRAP and iron chelating capacity assay. Active substances were detection, total phenolic, flavonoids and volatile compounds were analyzed. According to DPPH analyzes, the inhibition percentage was 48.57% for aqueous extract and 76.34% for methanol extract. The FRAP reduction capacity was determined as 3.32 mg/mL for aqueous extract and 11.75 mg/mL FESO4 for methanol extract. The total concentrations of phenolics and flavonoids were calculated as 64.08 - 35.29 mu g/mL and 146.84 - 555.66 mu g/mL in aqueous and methanol extracts, respectively. Finally, five volatile compounds were detected in methanol extracts. The results indicated that the endemic species of T. carvifolius can be evaluated as a natural antioxidant plant.