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Tyrosinase is the first and rate limiting enzyme in the synthesis of melanin pigments for coloring hair, skin, and eyes. As reported in this study, a natural product, (−)-N-formylanonaine isolated from the leaves of Michelia alba D.C. (Magnolianceae), was found to inhibit mushroom tyrosinase with an IC₅₀ of 74.3μM and to have tyrosinase and melanin reducing activities in human epidermal melanocytes without apparent cytotoxicity to human cells, superior to the known tyrosinase inhibitors, such as kojic acid and 1-phenyl-2-thiourea (PTU). Based on homology modeling, the compound binds the active site by coordinating with two Cu²⁺ ions. In addition, the compound had antioxidation activities in tests for scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH), reducing power, and chelating metal ions. To our knowledge, this is the first study to reveal the bioactivities of (−)-N-formylanonaine from this plant species.