Objective: The purpose of this study was to investigate the arginase inhibitory activity, antioxidant activity, and also pharmacognostical study of Sterculia macrophylla leaves. The main component of genus Sterculia was flavonoid that was well known to demonstrate arginase inhibitory activity. Methods: Sample was extracted gradually using n-hexane, ethyl acetate, and methanol solvents, subsequently. The n-hexane, ethyl acetate, and methanol extract were determined for their arginase inhibitory activity. The most active extract was methanol extract. This extract was determined for its antioxidant activity, arginase inhibitory activity, identification of chemical compound, chromatogram profile and determined the content of total flavonoid. The leaves and powder of Sterculia macrophylla were identified with microscopic and macroscopic evaluation. Results: The most active extract was methanol extract with IC50 114,659 μg/mL for arginase inhibitory activity and IC50 78.47 μg/mL for DPPH scavenging activity. The secondary metabolite of methanol extract presence compound of alkaloid, flavonoid, tannin, terpene, and glycoside. The total flavonoid content was 141.10 mg/gram extract. The star-shape trichoma was identified as a specific fragment. Conclusion: The methanol extract of Sterculia macrophylla showed activity as arginase inhibitor and antioxidant.