Drug delivery systems have been extensively developed to enhance the therapeutic efficacy of drugs by altering their pharmacokinetics and biodistribution. However, the use of high quantities of drug delivery systems can cause toxicity due to their poor metabolism and elimination. In this study, we developed polysaccharide-based drug delivery systems which exert potent therapeutic effects and could display synergistic therapeutic effects with drug payloads, leading to dose reduction. Cinnamaldehyde, a major component of cinnamon is known to induce anticancer activity by generating ROS (reactive oxygen species). We developed cinnamaldehyde-conjugated maltodextrin (CMD) as a polymeric prodrug of cinnamaldehyde and a drug carrier. Cinnamaldehyde was conjugated to the hydroxyl groups of maltodextrin via acid-cleavable acetal linkages, allowing facile formulation of nanoparticles and drug encapsulation. CMD nanoparticles induced acid-triggered ROS generation to induce apoptotic cell death. Camptothecin (CPT) was used as a model drug to investigate the potential of CMD nanoparticles as a drug carrier and also evaluate the synergistic anticancer effects with CMD nanoparticles. CPT-loaded CMD nanoparticles exhibited significantly higher anticancer activity than empty CMD nanoparticles and CPT alone in the study of mouse xenograft models, demonstrating the synergistic therapeutic effects of CMD with CPT. Taken together, we believe that CMD nanoparticles hold tremendous potential as a polymeric prodrug of cinnamaldehyde and a drug carrier in anticancer therapy.