Reaction of 1-methylimidazole with 3-(trimethoxysilyl)propyl chloride resulted in formation of 1-methyl-3-(trimethoxysilyl)propyl imidazolium chloride ([pmim]Cl). Anchoring of the ionic liquid on to silica-coated magnetic Fe 3 O 4 particles afforded the corresponding supported ionic liquid MNP-[pmim]Cl. Exchanging the Cl -anion by treatment with H 2 SO 4 gave the Brønsted ionic liquid MNP-[pmim]HSO 4 . FT-IR, XRD, SEM, TEM, TG/DTG, VSM, and CHN analysis were used to characterize the supported ionic liquid. The results indicated the catalyst was a nanostructure. The catalytic activity of the supported ionic liquid was examined in the synthesis of the polysubstituted pyridines by reaction of aromatic aldehydes, and acetophenones or indan-1-one with ammonium acetate under solvent-free conditions. The catalyst could be easily recovered, by applying an external magnetic field, and reused at least six runs without deterioration of its catalytic activity.