An orange-emitting, long-persistent phosphor, Ca2Si5N8:Eu2+,Tm3+, was developed. Afterglow of this phosphor decays more slowly than that of the conventional red-emitting, long-persistent phosphor, Y2O2S:Eu3+,Ti,Mg. After 420 nm excitation, the afterglow luminance is initially lower, but, after 8 min, gets higher than luminance of Y2O2S:Eu3+,Ti,Mg. Long afterglow results from electron traps formed by Tm3+ at the Ca2+ site. The origin of two main thermoluminescence glow peaks at 220 and 350 K is discussed based on their dependence on Eu or Tm concentration and Ca/Si atomic ratio. Increased thermoluminescence intensity is observed by excitation in Eu2+ 4f-5d transition at room temperature followed by the fundamental absorption of the host at low temperature.