Oxynitride-based phosphors CaSi2O2N2 codoped with Ce3+ and Eu2+ were prepared in this study. Broad Ce3+ excitation spectra ranging from 200 to 500 nm were found for Ca Si2O2N2:Ce3+, Eu2+ phosphors. The emission bands consisted of Ce-3 broken vertical bar and Eu-2 broken vertical bar emission peaks. When the Eu-2 broken vertical bar concentration increased, the emission intensity of Ce3+ decreased along with the enhancement in the Eu2+ emission intensity. The energy transfer from Ce3+ to Eu2+ occurred effectively in CaSi2O2N2: Ce3+, Eu2+ with a dipole-dipole interaction. The increased Eu-2 broken vertical bar concentration led the emitting colors of the prepared phosphor to shift from blue to green region. Increasing the temperature caused the emission intensity to decrease monotonously due to the thermal quenching effects.