Hyperpigmentation disorders are generally difficult to treat because of the limited availability of effective therapeutics with minimal side effects. In this issue, Lehraiki et al. report that metformin, an antidiabetic drug, inhibited melanogenesis, in vitro and in vivo, and they suggest that metformin may be used to treat hyperpigmentation disorders. This commentary reviews the molecular mechanisms through which metformin inhibits melanogenesis and examines metformin as a potential drug to treat hyperpigmentation.