Dyslipidemia is exemplified by high levels of low-density lipoprotein cholesterol (LDL-C) and represents a risk factor for cardiovascular diseases and requires therapeutic intervention. Several experimental studies suggest that bitter melon (Momordica charantia) improves lipid metabolism in animal models of dyslipidemia and diabetes. This study evaluated the effects of bitter melon extracts on lipid metabolism following a 30-day treatment period in Japanese adults. This randomized, double-blind, placebo-controlled trial included 43 adult volunteers who received either 100 mg of hot-water extracts of bitter melon (n = 23) or a placebo (n = 20) three times daily for 30 days. The body weight, blood pressure, and levels of LDL-C and other blood parameters of each subject were measured before and after the study period. The results showed that the intervention group exhibited significantly lower LDL-C levels (P = 0.02) as compared with the control group, and there were no significant changes in either group in terms of body weight, body mass index, systolic pressure, diastolic pressure, total cholesterol, high-density lipoprotein cholesterol, triglycerides, or blood glucose. These results suggested that bitter melon extracts might effectively lower LDL-C levels in humans and exhibit potential therapeutic value for the management of dyslipidemic conditions.