Objective: In this study, we investigated the protective molecular mechanisms of bitter melon under the free fatty acid-induced insulin resistance in human skeletal muscle cells and high fat/high fructose-fed mice. Methods: To clarify the effects of bitter melon on inflammation, free fatty acid was treated with or without bitter melon (MDE) in human skeletal muscle cells and several stress signaling pathways such as inflammation, endoplasmic reticulum (ER)-stress, and insulin signaling were measured using immunoblotting. To investigate the effects of MDE on insulin resistance and diabetes, C57BL/6J mice were randomly divided into two groups: 60% high fat and 30% high fructose diet group, and HF/HFr plus ethanol-extracted bitter melon diet group. To investigate the molecular mechanisms of bitter melon, we tested several signal pathways using immunoblotting. IPGTT (intraperitoneal glucose tolerance test), and ITT (Insulin tolerance test) were performed. Results: MDE ameliorated free fatty acid-induced insulin resistance through improved insulin signaling such as AKT and GSK in human skeletal muscle cells. Glucose up-take was also significantly recovered by MDE. In addition, MDE reduced free fatty acid-induced inflammatory signaling and several cytokines in human skeletal muscle cells. We demonstrated MDE was significantly effective for ameliorating HF/HFr diet-induced glucose intolerance, insulin resistance, and fatty liver. MDC significantly recovered insulin signaling and inflammatory cytokines such as IL6, TNF-a, MCP-1 in MDE treated mice compared to control mice. In addition, BME significantly reduced HF/HFr induced serum alanine transaminase (ALT) serum TG and serum free fatty acids in mice. All this data indicates BME has protective effects against free fatty acid-impaired insulin signaling in human skeletal muscle cells as well as in HF/HFr-induced mice. Conclusion: This study demonstrated bitter melon (momodica charantia) has protective effects on insulin resistance and diabetes in human skeletal muscle cells and HF/HFr diet mice.