CONTEXT: Other than weight reduction by dieting or physical activity, there are no well-documented medical treatments for fatty liver disease. OBJECTIVE: To evaluate the efficacy of the add-on Gynostemma pentaphyllum (GP) in research subjects with nonalcoholic fatty liver disease. DESIGN: A randomized, single-blind, controlled clinical trial. SETTING: Hospital-based clinic. PATIENTS: Fifty-six research subjects who were diagnosed with nonalcoholic fatty liver by abdominal ultrasound scanning. INTERVENTIONS: The treatment group and the control group followed a controlled diet for 2 months. After 2 months, the treatment group continued to diet and received 80 mL GP extraction for 4 months; the control group continued to diet and received a placebo capsule for 4 months. MAIN OUTCOME MEASURES: Body mass index (BMI), biochemistry data, and fatty liver score were measured at baseline, at 2 months, and at 6 months. RESULTS: After 2 months of dieting, BMI and most biochemistry data decreased in both study groups. There were no significant differences in BMI or biochemistry data at month 2 between the 2 study groups. At month 6, BMI, triglyceride, aspartate aminotransferase (AST), alanine aminotransferase, alkaline phosphatase, insulin (ALP), insulin resistance index (HOMA-IR), and fatty liver score were reduced in both groups. The treatment group saw significant reductions in BMI, AST, ALP, insulin, and HOMA-IR, however. Changes in uric acid levels in the 2 groups from month 2 to month 6 were statistically significant (P = .028) CONCLUSION: GP is an effective adjunct treatment to diet therapy for patients with nonalcoholic fatty liver disease.