A new carbon nanofibrous mat with necklace-like structures have been prepared by carbonization of cellulose/carbon black (CB) nanofibers through electrospinning of cellulose acetate/CB blend solution followed by deacetylation. The effect of carbon black on the thermal stability of the precursor and morphology of the CNFs were investigated using thermogravimetric analysis, field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy. The FE-SEM images showed that cellulose derived CNFs form matrix for accomplishing necklace-like fibers containing spherical CB nanoparticles with diameter between 30 and 60 nm after heating of cellulose/CB nanofibers. It is demonstrated that the incorporation of CB particles increases the electrical conductivity from 1.4 to 16 mS and carbon yield from 12 to 30%. Carbon nanofibers based on cellulose/CB was evaluated as a suitable adsorbent for removal of methylene blue (MB) from water. The final dye removal was found to be 97% at the initial MB concentration of 20 mg L-1. This study suggests a new carbon nanofiber structure that will be potentially useful for energy applications and water treatment.