While the reddish-orange emitting phosphors M2Si5N8:Eu2+(M=Ca, Sr) have been intensively investigated as potential materials for white-light-emitting diodes, in this study, optical energy storage properties of (Ca1-xSrx)(2)Si5N8: Eu2+, Tm3+ (x=0-1) solid solutions were tuned by cation substitution, which was commonly used to tune color point for improving w-LEDs. Partial substitution of either Ca by Sr or Sr by Ca resulted in a redshifted Eu2+ emission which had a demarcation point at x=0.5. Furthermore, the (Ca1-xSrx)(2)Si5N8: Eu2+, Tm3+ materials exhibited similar persistent- and photostimulated luminescence behaviors with a maximum intensity at about x=0.2. Such optical energy storage characters of the samples were attributed to the more appropriate trap depths (322-333K) and higher density of energy level traps indicated by the thermoluminescence analysis.