The phenolic contents and antioxidant activities of leaf extracts from Elaeocarpus submonoceras Miq. were determined for two alternative extractions, namely maceration with ethanol and successive extraction by Soxhlet, with various solvents. Ethanol extract showed the highest phenolic content and strong antioxidant activities against DPPH and ABTS, followed in rank order by methanol and ethyl acetate extracts. The ethyl acetate extract showed no cytotoxic effect towards HaCaT, a human skin non-carcinoma cell. Based on thin layer chromatography, cytotoxic and antioxidant activities, ethyl acetate extract was chosen for isolation. The structure of an isolated compound was identified as gallic acid from 1H-NMR. This study provides the first scientific information regarding the phenolic content and antioxidant activities of E. submonoceras Miq.