Cellulose nanofibers (CNFs) were prepared from sugarcane bagasse and used as reinforcement in epoxy nanocomposites. To obtain CNFs, the cellulose was bleached with sodium chlorite, hydrothermally hydrolyzed with 5% w/v oxalic acid under pressure of 800 psi at 100 A degrees C in a microwave reactor, and homogenized using a mechanical homogenizer. The diameters of CNFs determined from field emission scanning electron microscope (FE-SEM) vary from 8 to 86 nm. The percentage crystallinity obtained from X-ray diffractometry is 62.8%. The epoxy was mixed with the prepared CNFs and cured at room temperature for 7 days. The effects of CNFs concentrations (0, 0.5, 1.0, 3.0, 5.0 and 10.0 wt%, dry basis) on the tensile properties and scratch resistance of the nanocomposites were investigated. Young's modulus and tensile strength increased with an increasing CNFs loading up to 3 wt %. Above that concentration the tensile elongation at break increased; this was at the rate faster than the modulus decreased. The instantaneous and healing scratch depths and thus viscoelastic recovery were determined using a micro-scratch tester. The percentage recovery values are higher for the nanocomposites than for the pure epoxy.