Copper oxide nanoparticles (CuO NPs) have developed as a significant class of nanomaterial with potential dangers to organisms and the environment in a variety of applications. This study aimed to investigate the impact of costus root extract against CuO NPs induced oxidative stress, alterations in heart structure and functions. 40 adult male rats were assigned randomly to four groups: first; control, second; costus (300 mg/kg body weight/day) orally for 2 weeks, third; CuO NPs (100 mg/kg body weight/day) intraperitoneally for 4 weeks and fourth; CuO NPs + costus. Current results revealed, significant increases in serum levels of creatine kinase-MB, creatine kinase enzyme, lactate dehydrogenase, myoglobin, aspartate aminotransferase, alkaline phosphatase, cardiac TBIRS, total thiol, nitric oxide, and cardiac proliferating cell nuclear antigen after CuO NPs administration when compared with control group. Conversely, statistical significant decreases were detected in cardiac reduced glutathione, catalase, and superoxide dismutase in CuO NPs group as compared with control group. Interestingly, treatment of CuO NPs with costus root extract was associated with significant improvements of the studied parameters, heart structure and functions. CuO NPs-induced toxicity, injury and oxidative stress in rat heart and treatment with Costus root extract could scavenge free radicals producing beneficial effects against CuO NPs.