In the present work, yttrium aluminum garnet Y3Al5O12−xN2x/x (YAGN) was obtained using aluminum nitride (AlN) as a source of aluminum. YAGN was doped with the Ce3+ ions (YAGN:Ce) in concentrations from 0.5 to 14 mol%. According to XRD analysis, the crystal structure of YAG is maintained with traces of Al2O3. Scanning electron microscope (SEM) studies showed that the nitrogen atoms are not quite uniformly incorporated into grains, which may easily lead to the formation of a number of various Y3+ sites. This means that Ce3+ ions can also occupy sites of different nitrogen/oxygen ratios. The probability of Ce3+entering different sites changes with the dopant concentration. The emission and excitation spectra of Ce3+ exhibit concentration dependence. For concentrations in the range 0.5–7% emission bands are extended to longer and shorter wavelengths in comparison to the typical emission of Ce3+ in YAG. With the increase in the concentration of active ions (10–14 mol%) excitation bands show further widening, and the emission bands shift gradually toward longer wavelengths, reaching the value of 45 nm for 14 mol%. The usefulness of these phosphors for application in white LED technology is discussed on the basis of the quantum efficiency of the emissions, luminescence decay times, and thermal quenching of the Ce3+ emission.