A microwave-assisted hydrothermal route was developed for preparing (Sr1−xyCexTby)Si2O2−δN2+μ phosphors. Both the required calcination temperatures and heating duration were markedly reduced as compared with the solid-state reaction. With a rise in the calcination temperatures, the emission intensity of Ce3+-doped phosphors decreased due to the thermal quenching effects. For Tb3+-doped phosphors, the emission intensities of the splitting peaks were influenced by the thermal interaction between the Tb3+ energy levels. It is found that the Ce3+- and Tb3+-doped SrSi2O2N2 phosphors demonstrate great absorption in the vacuum ultraviolet region and are therefore suitable for application in plasma display panels. While Ce3+ and Tb3+ were codoped into SrSi2O2N2, the emission spectra exhibited the combination of the Ce3+ and Tb3+ emission peaks. The energy transfer process from Tb3+ to Ce3+ via the electrostatic interaction was also investigated in detail.