Kendomycin is a small-molecule natural product that has gained significant attention due to reported cytotoxicity against pathogenic bacteria and fungi as well as a number of cancer cell lines. Despite significant biomedical interest and attempts to reveal its mechanism of action, the cellular target of kendomycin remains disputed. Herein it is shown that kendomycin induces cellular responses indicative of cation stress comparable to the effects of established iron chelators. Furthermore, addition of excess iron and copper attenuated kendomycin cytotoxicity in bacteria, yeast, and mammalian cells. Finally, NMR analysis demonstrated a direct interaction with cations, corroborating a close link between the observed kendomycin polypharmacology across different species and modulation of iron and/or copper levels.