Garcinia hombroniana Pierre leaves extract have been known to contain flavonoid, but it has not been known yet for its antioxidant activity and inhibition of lipoxygenase activity. This study aims to determine antioxidant activity tested by using FRAP (Ferric Reducing Antioxidant Power) method and inhibition of lipoxygenase activity of G. hombroniana leaves extract using baicalein as the positive control. Total flavonoid assay is also quantitatively done by AlCl₃ colorimetric method on the most active extract using quercetin as the positive control. The test result showed that the n-hexane, ethyl acetate and methanol extract of G. hombroniana Pierre leaves have antioxidant activity which showed by EC₅₀ value​​ consecutively are 36.260; 2.969; and 7.416 μg/mL, and also can inhibit lipoxygenase activity which showed by IC₅₀ value consecutively are 2.052; 0.134; and 1.314 μg/mL. Ethyl acetate extract of G. hombroniana Pierre leaves has the most active antioxidant activity and inhibition of lipoxygenase activity. Total flavonoid content of ethyl acetate extract of G. hombroniana Pierre leaves is 42.004 mg QE/g sample. Garcinia hombroniana Pierre leaves extract has antioxidant activity and can inhibit lipoxygenase activity.