Objective: This study aims to determine the inhibitory activity of Garcinia xanthochymus mesocarp extracts against 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase.Methods: G. xanthochymus mesocarp was macerated sequentially using n-hexane, ethyl acetate, and methanol. Phytochemical screening andquantification of total flavonoids were performed on the most active extract.Results: Based on the tests, n-hexane, ethyl acetate, and methanol extracts had inhibitory activities of 12.30±1.098%, 55.63±10.584%, and44.01±1.053%, respectively. The results showed that the ethyl acetate is the most active extract, containing flavonoid, terpenoid, glycoside, andanthraquinone compounds. The amount of total flavonoid contained in ethyl acetate extract was 1.61% or 16.114 mg QE/g toward quercetin.Conclusion: The n-hexane, ethyl acetate, and methanol extracts of G. xanthochymus have inhibitory actions against HMG-CoA reductase activityin vitro. Further research is still needed to strengthen this finding.