Reaction of the tricopper­(I)–dinitrogen tris­(β-diketiminate) cyclophane, Cu3(N2)­L, with O-atom-transfer reagents or elemental Se affords the oxido-bridged tricopper complex Cu3(μ3-O)­L (2) or the corresponding Cu3(μ3-Se)­L (4), respectively. For 2 and 4, incorporation of the bridging chalcogen donor was supported by electrospray ionization mass spectrometry and K-edge X-ray absorption spectroscopy (XAS) data. Cu L2,3-edge X-ray absorption data quantify 49.5% Cu 3d character in the lowest unoccupied molecular orbital of 2, with Cu 3d participation decreasing to 33.0% in 4 and 40.8% in the related sulfide cluster Cu3(μ3-S)­L (3). Multiedge XAS and UV/visible/near-IR spectra are employed to benchmark density functional theory calculations, which describe the copper–chalcogen interactions as highly covalent across the series of Cu3(μ-E)3+ clusters. This result highlights that the metal–ligand covalency is not reserved for more formally oxidized metal centers (i.e., CuIII + O2– vs CuII + O–) but rather is a significant contributor even at more typical ligand-field cases (i.e., Cu3 II/II/I + E2–). This bonding is reminiscent of that observed in p-block elements rather than in early-transition-metal complexes.