Ternary nanocomposites based on Fe3O4@C core@shell nanoparticles encapsulated in polyaniline were synthesized by using an efficient, two-step procedure and used as supercapacitor electrode materials for the first time. The morphology of the resulting Fe3O4@C@PANi nanocomposites was characterized by transmission electron microscopic measurements, and further structural insights were obtained by Raman, X-ray diffraction, and X-ray photoelectron spectroscopic studies. In electrochemical measurements, the resulting Fe3O4@C@PANi electrode exhibited a high specific capacitance of 420 F g(-1) at 0.5 A g(-1) as well as an energy density of 32.7 Wh kg(-1) at the power density of 500 W kg(-1). Additionally, the Fe3O4@C@PANi electrode showed excellent long-term stability with 82% retention of the capacitance after 5000 cycles at 10 A g(-1). These results suggest that Fe3O4@C@PANi-based supercapacitors may serve as high-rate energy storage systems.