Direct evidence for energy transfer from cuprous diimine excited states(s) is reported for the first time. Visible excitation of Cu(dpp)(2)(PF6) (dpp is 2,9-diphenyl-1,10-phenanthroline) or Cu(dmp)(2)(PF6) (dmp is 2,9-dimethyl-1,10-phenanthroline) produces long-lived metal-to-ligand charge-transfer excited states which are quenched by the addition of anthracene. Stern-Volmer analysis yields energy transfer rates of (2.8 +/- 0.2) x 10(7) M(-1) S-1 from Cu(dpp)(2)(+)* and (2.0 +/- 0.2) x 10(8) M(-1) s(-1) from Cu(dmp)(2)(+)* to anthracene. The appearance of the triplet-to-triplet absorption of anthracene following excitation of the copper phenanthroline compounds confirms that the quenching mechanism is energy transfer. The efficiency of energy transfer from Cu(dmp)(2)(+)* to anthracene is about 1/4 that of the well-known Ru(bpy)(3)(2+)* sensitizer.