In this study we report the synthesis of undoped and Sc 3+ doped Bi 2Fe 4O 9 nanoparticles using sonochemical technique. X-ray diffraction reveals that all samples are single phase with no impurities detected. EDS analysis was done to confirm the extent of Sc 3+ doping in the samples. The size and morphology of the nanoparticles have been analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Bi 2Fe 4O 9 nanoparticles show a weak ferromagnetic behavior at room temperature, which is quite different from the linear M-H relationship reported for bulk Bi 2Fe 4O 9. A magnetization of 0.144 μB/f.u. is obtained at 300 K, which is mainly attributed to the uncompensated moments at the disordered particle surface resulting from the reduced coordination of the surface spins, arising due to lattice strain or oxygen deficiency. Addition of Sc 3+ dopant in varying concentrations in these Bi 2Fe 4O 9 nanoparticles, improves their magnetic as well as ferroelectric properties. The leakage current is considerably reduced and electric polarization increases significantly in case of Bi 2Fe 4(1-x)Sc xO 9 (x = 0.1) nanoparticles. Thus it can be inferred that Sc 3+ doped Bi 2Fe 4O 9 nanoparticles shows promise as good multiferroic materials. © 2012 Elsevier B.V. All rights reserved.