Nanoparticles of BaLiF3:Er3+ were prepared from the quaternary microemulsions of Cetyltrim-Enthyl Ammonium Bromide (CTAB), n-butanol, n-octane, and water, using the hydrothermal-microemulsion technique. The complex fluorides were characterized by means of X-ray power diffraction, Environmental Scanning Electron Microscopy (ESEM), and fluorescence spectra. The positions and intensities of the peaks in the XRD pattern of the final products indicate the formation of BaLiF3:Er3+. No other peaks or impurities were detected. The average size of the nanoparticles, calculated with the Debye-Scherrer equation was 98.45 nm, which was in agreement with the result of ESEM. The infrared fluorescence spectra consisted of four peaks with a predominant peak located at 1540 nm.