Ternary copper(II) complex, structurally characterized as [Cu(phen)(met)(MeOH)](ClO4) (1) by X-ray crystallography, has 1,10–phenanthroline (phen) as an intercalator/binder to supercoiled pUC19 DNA and L-methionine (met) as a photosensitizer, and the complex displays efficient photonuclease activity on irradiation with UV (312 nm) or visible (436, 532 nm) light through a mechanistic pathway involving singlet oxygen.