Here, we report the scintillation properties of LaBr3?xIx:5%Ce3+ with four different compositions of x, i.e., x = 0.75, 1.5, 2, and 2.25. Radioluminescence spectra reveal a shift of the emission wavelength with the LaBr3 to LaI3 ratio. LaBr1.5I1.5:5%Ce3+ shows the highest scintillation light yield of 58?000?photons/MeV, whereas LaBr0.75I2.25:5%Ce3+ shows the fastest scintillation decay time of 12 ns under 662 keV ?-ray excitation. This decay time is faster than that of 16 ns in LaBr3:Ce3+. The temperature dependence of radioluminescence spectra is presented. The structures and lattice parameters of the materials were determined from powder x-ray diffraction.