The two four-coordinate N-heterocyclic carbene (NHC) copper(I) complexes, [Cu(Ph-BenIm-methylPy)(POP)]PF₆ (1), and [Cu(Ph-Im-methylPy)(POP)]PF₆ (2) Ph-BenIm-methylPy = 3-benzyl-1-(6-methyl-pyridin-2-yl)-1H-benzimidazolylidene, Ph-Im-methylPy = 3-benzyl-1-(6-methyl-pyridin-2-yl)-1H-imidazolylidene, POP = bis[2-diphenylphosphino]-phenyl)ether) have been synthesized and characterized. Those complexes exhibit blue to green emission with very high quantum yields and long excited-state lifetimes. The experimental results reveal that the origin of emissive state at room temperature occurs from the combination of TADF and phosphorescence in which phosphorescence predominates TADF, and the corresponding emissive mechanisms were discussed. To the best of our knowledge, the combined emissions with high quantum yield close to ca. 100% have not been previously reported in this library of the four-coordinate NHC-Cu(I) complexes.