Cellulose is considered one of the most important renewable sources of biopolymers on Earth. It has attracted widespread attention due to its physical–chemical characteristics, such as biocompatibility, low toxicity, biodegradability, low density, high strength, stability in organic solvents, in addition to having hydroxyl groups, which enable its chemical modification. In this study, cellulose nanofibrils (CNFs) were functionalized with dicyanovinyl groups through nucleophilic vinylic substitution (SNV) and used as electrocatalyst in electrochemical of carbon dioxide (CO2) reduction. Results indicate that introducing dicyanovinyl groups into the structure of nanocellulose increases electrocatalytic activity as compared to that of pure nanocellulose, shifting the onset potential of the electrochemical CO2 reduction reaction to more positive values as compared to those for the reaction with argon. The atomic force microscopy (AFM) images show no changes in the morphology of CNFs after chemical modification.