In this work, cellulose nanoparticles (CNP) reinforcement on synthetic rubber (SR)/polylactic acid (PLA) blend was investigated. Initially, SR/PLA blend was prepared by varying SR from 5 to 20 wt%. Later, a fixed amount (3 wt%) of CNP was added and resulting effect on mechanical, thermal, and dynamic properties was studied. The results show the addition of CNP in SR/PLA blend resulted in similar to 147 and similar to 196% improvement in tensile strength and storage modulus, respectively. In addition, impact strength of SR/PLA blend was almost doubled after CNP incorporation. An improvement of similar to 4.5% in the thermal stability of SR/PLA was also observed.