Thin films of cerium-activated alkaline earth thiogallate were investigated for the fabrication of blue-emitting thin-film electroluminescent (TFEL) devices. The films were prepared by RF sputtering from targets with composition : M1-xGa2S4:Cex, where M = Ba, Ca, Sr, and 0.01 less-than-or-equal-to x less-than-or-equal-to 0.1. Photoluminescent (PL) emission spectra showed matching peak wavelengths to those obtained from electroluminescent (EL) emission for each alkaline earth thiogallate film. The optimum cerium concentration for EL emission intensity for strontium and calcium thiogallate films was determined to be x = 0.04 and 0.06, respectively. The EL brightness measured for the calcium thiogallate devices was almost twice that measured for the strontium thiogallate devices. This brightness variation, however, is due mainly to the difference in the lumen equivalent of the emission intensity. The cerium concentration dependence of the PL emission spectra of the thiogallate films is substantially decreased compared with the respective powder material suggesting inhomogeneous cerium incorporation in the films.