Bitter melon (BM, Momordica charantia L) has various biological functions including antidiabetic, anticancer, anti-inflammatory, antiviral, and antioxidant activities. In this study, the antioxidant effects of BM fruits, leaves, stems, and roots after roasting using DPPH, ABTS, reducing power, and ferric reducing/antioxidant power (FRAP) assays were compared. The roasted BM exhibited significantly higher antioxidant activity than unroasted BM in the test methods used. Particularly, the roasted BM roots showed the highest antioxidant activity compared to any other extracts. Antioxidant compounds including flavan-3-ols and phenolic acids increased, whereas flavanols decreased in the BM following roast processing. Moreover, the total phenolic contents and flavan-3-ol and phenolic acid contents were markedly increased, leading to a general increase in antioxidant activities after roasting. These results suggest that the roasting BM extracts could be used as a potential source of natural antioxidants in certain food and medicinal applications.