The influence of the Ce3+ concentration on the cathodoluminescence (CL) characteristics of SrAl12O19:Ce-x(3+),Eu-0.01(2+) (x = 0.01-0.09) was studied. At 1 mol% cerium in SrAl12O19:Ce-x(3+), Eu-0.01(2+) (x = 0.01), two broad emission bands centered at 320 nm and at about 400 nm were observed. The intensity of Ce3+ emission at 320 nm decreased as the Ce3+ concentration increased, whereas the intensity of the emission band at 400 nm increased with increasing Ce3+ concentration at fixed Eu2+ concentration. At low concentration of Ce3+ (x = 0.1-0.5), the Ce3+ emission intensity decreased with the Eu2+ emission intensity being enhanced due to the energy transfer from Ce3+ to Eu2+. In high concentrations of Ce3+ (x = 0.07, 0.09), the cross-relaxation processes between nearest Ce3+ ions led to the diminishing intensity of Ce3+ emission, because of the limited energy accepters, i.e., Eu2+ ions, which resulted in a single emission band at about 400 nm.