Cellulose nanowhiskers were prepared by acid hydrolysis of drumstick fruit fibers from Moringa oleifera. It was incorporated into thermosetting epoxy matrix at various weight fractions (0.06, 0.12 or 0.18 wt%) to investigate their effect on the mechanical and thermal properties of resulting epoxy resin composite. Drumstick fruit nanofibers slightly increased the thermal stability of the prepared composites. The tensile modulus (31.4%) and bending modulus (38.2%) of the epoxy composites filled with 0.18 wt% cellulose nanowhiskers significantly increased in comparison with that of the neat cured epoxy resin. However, the tensile strength (48.7%) and bending strength (41.6%) of the composites significantly decreased as the 0.18 wt% nanowhiskers were added into the epoxy matrix. The nanowhiskers (0.18 wt%) can be efficiently used in the epoxy matrix to improve considerably the tensile and bending modulus of the composites as well as a slight increase in the thermal stability.