In this study, a novel extraction method has been employed to obtain highly efficient cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) from waste hemp fibers with maximum potential. By applying alkali and bleaching treatment methods, the eradication of hemicelluloses and lignin with purified cellulose was achieved. Morphological studies confirmed that the purification and isolation of cellulose as a network of nanofibers were achieved. as the as-prepared CNFs were employed as the economic and environment-friendly candidate for reinforcing epoxy-carboxyl-terminated poly(butadiene-co-acrylonitrile) (CTBN) blend, for the first time. The adhesive strength of the epoxy/CTBN blend enhanced significantly (34%) with the incorporation of 0.5 phr of CNFs. The study has confirmed that on addition of a very small concentration of CNFs (0.25 phr) in the epoxy/CTBN thermosets, thermal stability, storage modulus, tensile shear adhesive, and impact strengths of epoxy/CTBN blend improved because of the excellent properties of the CNF. The adhesive strength of the epoxy/CTBN blend enhanced from 2.67 +/- 0.19 MPa to 3.34 +/- 0.06 and 3.59 +/- 0.12 through the incorporation of 0.25 and 0.5 phr CNF, respectively.