Electrospun nanofibrous composites were prepared from polyacrylonitrile yarn waste (PAN) and carboxylic group functionalized multiwall carbon nanotubes (COOH-MCNT) with 0.5, 1.0 and 1.5% (w/w). The higher thermal stability of nanofibres was confirmed using Thermo Gravimetric Analysis (TGA). The presence of carboxyl group was confirmed by Fourier transform infrared (FT-IR) analysis. Scanning Electron Microscope (SEM) results confirmed the rough and irregular surface of nanofibres. The adsorption capacity of the PAN-COOH-MCNT nanofibrous composites were evaluated systematically with methylene blue (MB) as an adsorbate. The adsorption studies were conducted with various physical and chemical parameters such as contact time, solution pH and initial dye concentration. The nanofibrous composite was acquired the maximum amount of methylene blue dye removal under basic pH (10) at initial dye concentration of 30 mg/L. The pseudo second order kinetic model was found to be most fitted for the adsorption of methylene blue with higher R2 value (0.993). The external diffusion model was adapted to understand the diffusion mechanism of adsorption. It was observed that the Freundlich and Scatchard isotherm models are more favourable for the adsorption of methylene blue. The prepared PAN/COOH-MCNT nanofibrous composite was a potential adsorbent for the removal of methylene blue dye.