A new Ce3+-activated thiosilicate phosphor, BaLa 2Si2S8:Ce3+, was synthesized by using solid-state methods in a fused silica ampule and found to crystallize in the structure type of La2PbSi2S8. The crystal structure has been characterized by synchrotron X-ray diffraction and refined with Rietveld methods. This novel cyan-emitting phosphor can be excited over a broad range from UV to blue light (380-450 nm) and generates a broadband emission peaking at 471 nm with a quantum efficiency of 36%. Nonradiative transitions between Ce3+ ions in BaLa2Si2S 8:Ce3+ have also been demonstrated to be attributable to dipole-dipole interactions, and the critical distance was calculated to be 17.41 Å. When BaLa2Si2S8:Ce3+ phosphor was utilized to incorporate with yellow-emitting (Sr,Ca) 2SiO4:Eu2+ phosphor and red-emitting CaAlSiN3:Eu2+ phosphor on a 430 nm blue LED chip, a warm white light LED device with color rendering index of ∼96 was obtained. The results indicate that cyan-emitting BaLa2Si2S 8:Ce3+ can serve as a potential phosphor for incorporation in fabrication of solid-state lighting. The preparation, spectroscopic characterization, quantum efficiency, decay lifetime, thermal-quenching behavior, and related LED device data are also presented.