The use of ionic liquids (IL) and nanoparticles in polymeric membranes is known to increase the electrochemical performance for heavy metal ions must be eliminated from water resources. In this study at first, NiFe2O4 and Fe3O4 nanoparticles were obtained using cationic surfactants cetyltrimethylammonium bromide (CTAB) at 120°C in autoclave. Hybrid structure of this nanoparticles obtained by the method known as the hydrothermal was prepared with polybenzimidazole (Poly[2,21‐(p‐phenylene)‐5,51‐bis(benzimidazole)]: PBI1 and (Poly[2,21‐(p,p1‐diphenylene)‐5,51‐bis(benzimidazole)]: PBI2) in IL (1‐butyl‐3‐methylimidazolium bromide [BMIM]BF4: IL) environment. For the acquisition of hybrid nanoparticles with polybenzimidazole, polycondensation reaction of hydroxamoyl chloride (Terephtalohydroxamoyl chloride and 4,41‐Bis(phenylhydroxamoyl chloride) and 3,31‐diaminobenzidine monomers in IL environment was performed without acid media. The increase in proton conduction in comparison to the PBI membranes were observed due to the presence of ILs in PBI‐ILs blend membranes. These nanohybrids were characterized by the FT‐IR, XRD, TEM, EDX, at different temperature, vibrating sample magnetometer, and SEM analyses. Fourier transform infrared spectroscopy, and X‐ray diffraction, and the hybrid microspheres were found uniformly dispersed in the polymer matrices without any agglomeration. The influence of [BMIM]BF4 as IL on the structure, electrical conductivity and magnetic properties of PBI‐NiFe2O4‐IL nanocomposite were studied in detail. TGA analyses were performed for thermal resistance of nanoparticles and PBI hybrid structure. Tinitial, Tmax, and Tlast decomposition temperatures were determined, initial decomposition temperature was obtained in the range of 420–600°C for hybrid structures. POLYM. COMPOS., 39:4372–4385, 2018. © 2017 Society of Plastics Engineers