A reaction mechanism for the copper(I)-catalyzed oxidative aerobic trifluoromethylation of terminal alkynes has been determined by DFT calculations. The transmetalation of CF₃^– to copper appears to be a ligand replacement process independent of the metal. The dioxygen activation follows the sequence η¹-superoxocopper(II), μ-η²:η²-peroxodicopper(II) and bis(μ-oxo)-dicopper(III).