The current research discusses the efforts to achieve yarns coated with composite nanofibers and investigates some of their properties. Polyacrylonitrile/dimethyl formamide solutions containing various mass concentrations of single-wall and multiwall carbon nanotubes (SWCNTs and MWCNTs) and also functionalized SWCNTs were electrospun onto an acrylic staple yarn to produce hybrid yarns. The effect of the CNT addition on the final morphologies of the nanofibers was evaluated using SEM. The fibers prepared with higher CNT concentrations had larger diameters than those of fibers obtained by lower concentrations. The SEM, the optical microscope, and the microtome were used to investigate the structural morphology of the hybrid yarns. The conductivity and the viscosity of the solutions at different SWCNT concentrations were measured. The surface electrical resistance and the mechanical properties of the hybrid yarns composed of the nanofibers as sheath were analyzed. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 1143-1151, 2013