In this study we have prepared (polyacrylonitrile) PAN/iron oxide composite nanofibers by three different methods and have compared their removal efficiency for the adsorption of Congo Red (CR) dye from aqueous solution. In the first method, we have prepared electrospun PAN/iron(III) acetylacetonate composite nanofibers by electrospinning followed by a hydrothermal method for in situ growth of iron oxide nanoparticles on the surface of PAN nanofibers. In the second method the electrospun PAN nanofibers were immersed into the iron alkoxide solution followed by a hydrolysis reaction at 80 °C. In the third method, PAN/iron oxide composite nanofibers were prepared by blending the previously prepared iron oxide nanoparticles with the PAN solution followed by an electrospinning technique. The obtained different nanocomposite fibers were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR), X-ray diffraction (XRD), and Field Emission Scanning Electron Microscopy (FE-SEM) analytical techniques. The FE-SEM images clearly show the formation of iron oxide nanoparticles that are uniformly decorated on the surface of PAN nanofibers after hydrothermal reactions. The average diameters of the nanoparticles are observed to be in the range of 30 to 120 nm. The adsorption experiments such as effect of pH, contact time, initial concentration variation, and temperature were explored in the batch experiments. CR dye is used as a model organic pollutant for an adsorption study. An adsorption isotherm, kinetic study and thermodynamic study were also carried out to elucidate the adsorption mechanism.