This work demonstrates the preparation of polyacrylonitrile (PAN) based activated carbon nanofibers (ACNFs) through electrospinning followed by thermal treatment. Resulted activated carbon nanofibers having diameters in the range of 240-280 nm were then examined for the adsorption capability for methylene blue dye from aqueous solution. Batch mode experiments were carried out at room temperature to study the effect of amount of nanofiber, contact time and pH on dye adsorption. It was found that activated carbon nanofibers showed remarkable adsorption efficiency while completely decolorizing the dye solution within 60 min of contact. Results revealed that the adsorption data followed Langmuir isotherm giving maximum adsorption capacity of 72.46 mg/g and pseudo second order kinetic model. Furthermore, the reusability of activated carbon nanofibers had shown removal efficiency more than 80% up to 3 cycles. Morphology and structure of PAN nanofibers and ACNFs were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR). (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.