Sm3+-doped magnetite (Fe3O4) nanoparticles were synthesized through a one-pot facile electrochemical method. In this method, products were electrodeposited on a stainless steel (316L) cathode from an additive-free 0.005 M Fe(NO3)(3)/FeCl2/SmCl3 aqueous electrolyte. The structural characterizations through X-ray diffraction, field-emission electron microscopy, and energy-dispersive X-ray indicated that the deposited material has Sm3+-doped magnetite particles with average size of 20 nm. Magnetic analysis by VSM revealed the superparamagnetic nature of the prepared nanoparticles (Ms = 41.89 emu g(-1), Mr = 0.12 emu g(-1), and H (Ci) = 2.24 G). The supercapacitive capability evaluation of the prepared magnetite nanoparticles through cyclic voltammetry and galvanostat charge-discharge showed that these materials are capable to deliver specific capacitances as high as 207 F g(-1) (at 0.5 A g(-1)) and 145 F g(-1) (at 2 A g(-1)), and capacity retentions of 94.5 and 84.6% after 2000 cycling at 0.5 and 1 A g(-1), respectively. The results proved the suitability of the electrosynthesized nanoparticles for use in supercapacitors. Furthermore, this work provides a facile electrochemical route for the synthesis of lanthanide-doped magnetite nanoparticles.