In this study, different doses (control (0), 0.5, 5, 50 mg/kg b.w./day) of CuO nanoparticle (NP) were administered to female rats via oral gavage for 14 days. Following the exposures, the activities of ATPases in the kidney, brain and small intestine and activity of acetylcholinesterase (AChE) in the brain were measured. Levels of different glutathione forms (total GSH, rGSH, GGSG) and TBARS (thiobarbituric acid reactive substances) were also measured in the liver of rats. The accumulation of CuO NPs in the tissues were demonstrated following capture of tissue images by a transmission electron microscope (TEM). Data demonstrated that activity of AChE in the brain decreased significantly (P<0.05). ATPase activity in the brain and small intestine did not change significantly (P>0.05), though there were significant decreases (P<0.05) in ATPase activity in the kidney. Levels of glutathione forms did not change significantly, except the highest dose. Similarly, levels of TBARS increased significantly (P<0.05) at the highest dose. TEM images showed that CuO NPs were able to accumulate in the tissues, emphasizing occurred alterations in enzymatic and non-enzymatic biomarkers were due to CuO NP accumulation in the tissues.