In this work, we studied the effect of different pH values on morphology, band gap and photoluminescence (PL) properties of Eu³⁺/Tb³⁺ co-doped ZnO prepared by coprecipitation method. Experimental results show that alkaline condition is more favorable for the doping of Eu³⁺ and Tb³⁺ ions which reduce the band gap and increases the PL intensity of UV emission (385 nm) and visible emission (400—600 nm) of ZnO. Gaussian deconvolution PL spectra show that the defects on the surface of ZnO are decreased when it is synthesized under alkaline conditions. Furthermore, both the intrinsic orange emission of Eu³⁺ ions (611 nm) and the intrinsic green emission of the Tb³⁺ ions (495 nm) of ZnO in this case are obtained at the same time. High intensity green and orange emission indicates that Eu³⁺/Tb³⁺ co-doped ZnO is a promising PL material and has potential in emission devices.