Awareness of the environmental implications of conventional reinforcing fillers and the urge to reduce the carbon footprint have lead researchers to focus more on natural and sustainable materials. Nanocellulose from multitudinous sources finds use in elastomer engineering because of its distinctive properties, such as renewability, sustainability, abundance, biodegradability, high aspect ratio, excellent mechanical properties, and low cost. Green alternatives for conventional fillers in elastomer reinforcing have gained considerable interest to curb the risk of fillers from nonrenewable sources. The differences in properties of nanocellulose and elastomers render attractiveness in the search for synergistic properties resulting from their combination. This review addresses the isolation techniques for nanocellulose and challenges in its incorporation into the elastomer matrix. Surface modifications for solving incompatibility between filler and matrices are discussed. Processing of nanocomposites, various characterization techniques, mechanical behavior, and potential applications of nanocellulose elastomer composites are also discussed in detail.