The Tb3+/Eu3+ co-activated CaSnO3 nano-phosphors have been prepared by a sol-gel technique. The emission and excitation spectra as well as the luminescence decay behaviors were investigated. When excited at 378 nm, CaSnO3:Tb3+ phosphors exhibit green-emitting color with the strongest peak at 542 nm. After increasing the contents of Eu3+, the emitting color of the co-activated CaSnO3 phosphors presents varied hues from green through white and eventually to red by energy transfer (ET) from Tb3+ to Eu3+. The mechanism of ET has been determined to be a quadrupole-quadrupole interaction. The results indicate that CaSnO3:Eu3+, Tb3+ might be served as an UV-convertible color-tunable phosphor.