Orthorhombic structure of lanthanum ferrite nanoparticles (LaFeO3 NPs) with perovskite type phase has been synthesized with water-in-oil (W/O) microemulsion consisted of water/dioctyl sulfosuccinate sodium (aerosol-OT)/isooctane at room temperature. It has been shown that aerosol-OT reverse microemulsion solution is appropriate for synthesizing perovskite LaFeO3 NPs in the absence of any co-surfactants. Field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), energy dispersive analysis of X-ray (EDAX), X-ray diffraction (XRD), ultraviolet visible absorption spectroscopy (UV-Vis), and Fourier transform infrared spectroscopy (FT-IR) have been adopted for characterization of surface morphology, size, phase composition, structure, and optical properties of the considered NPs. Furthermore, the optical properties of LaFeO3 NPs have been further analyzed via photoluminescence (PL) spectroscopy. As shown by the physicochemical characterizations, our prepared NPs via aerosol-OT reverse microemulsion solution are spherical and nearly uniform (with a size of about 24.65 nm). Besides, they include an orthorhombic phase while no impurities are observed. Single phase lanthanum ferrite NPs have successfully been prepared at 500 degrees C. Moreover, UV-Vis spectrum indicates that the LaFeO3 NPs synthesized through this technique can be considered as a type of photocatalytic materials. (C) 2013 Elsevier Ltd. All rights reserved.