Cancer cells are more vulnerable to reactive oxygen species (ROS)-mediated oxidative stress than normal cells due to disturbed redox balance. It can be postulated that ROS-generating drug carriers exert anticancer actions, leading to combination anticancer therapy with drug payloads. Here, we report a ROS-generating polyprodrug of cinnamaldehyde (CA) that not only serves as a drug carrier but also synergizes with drug payloads. The polyprodrug of CA (pCA) incorporates ROS-generating CA in the backbone of an amphiphilic polymer through an acid-cleavable acetal linkage. pCA could self-assemble with tumor-targeting lipopeptide (DSPE-PEG-RGD) and encapsulate doxorubicin (DOX) to form T-pCAD micelles. At acidic pH, T-pCAD micelles release both CA and DOX to exert synergistic anticancer actions. Animal studies using mouse xenograft models revealed that T-pCAD micelles accumulate in tumors preferentially and suppress the tumor growth significantly. Based on the oxidative stress amplification and acid-responsiveness, ROS-generating pCAD micelles hold tremendous potential as drug carriers for combination anticancer therapy.