A growing body of research has now firmly established that the dietary intake of berry fruits has a positive and profound impact on human health, performance, and disease. These health benefits are believed to arise mainly from their antioxidant activities. Ma mao (Antidesma thwaitesianum Muell.) and mulberry (Morus alba Linn.) are tropical “berry-type” fruits which are commercially cultivated and commonly consumed in fresh and processed forms in North Thailand. These fruits have recently been reported to exhibit antioxidant abilities, but the phytochemicals contributed to their health benefits have not yet been clarified. The present study used high-performance liquid chromatography with a diode array detector and a mass spectrometry detector (HPLC-DAD/MSD) to identify and quantify the phenolic contents of ethanol fruit extracts of ma mao and mulberry. Total flavonoid, proanthocyanidin, including antioxidant potentials were also evaluated and compared between the two berry fruits. HPLC-DAD/MSD revealed the presence of catechin, quercetin, gallic acid and kaempferol (350.36, 3.60, 13.62 and 2.43 mg/kg dry wt, respectively) in ma mao, while the only phenolic content identified from mulberry was quercetin (38.11 mg/kg dry wt). Ma mao demonstrated significantly lower amount of total flavonoid (2.07±0.04 g/100g dry wt), but higher total proanthocyanidin (39.25±1.15 g/100g dry wt) than those detected from mulberry (4.17±0.05 and 18.92±2.13 mg/100g dry wt, respectively). In addition, ma mao showed significantly greater antioxidant potency compared to mulberry, as assessed by ABTS (0.32±0.01 vs 0.20±0.01 mM trolox equivalent/g respectively), DPPH in term of % inhibition (38.97±0.07 vs 25.61±0.72, respectively) and FRAP (36.99±0.30 vs 21.87±0.44 mM trolox equivalent/g, respectively). The present findings imply that the beneficial impact on human health and disease is much greater in ma mao than that of mulberry.