Nickel oxide nanoparticles (NiO-NPs) have wide application prospects in the technology and biomedicine fields. As a result, increased human and animal exposure to these nanoparticles through various routes raises health concerns. The present experiment aims to investigate the potential ameliorative role of thyme oil (TO) against disturbances of some hepatic and renal parameters caused by NiO-NPs in laboratory rats. Randomly, thirty-two adult rats were distributed into 4 groups, first group was a negative control and the remaining three groups were set for treatment through oral gavage for a period of 28 consecutive days. Treatment groups received the following: NiO-NPs (100 mg/kg), TO (5 mg/kg), NiO-NPs plus TO in the same amounts as mentioned. The results confirmed that intoxicated rats with NiO-NPs showed a considerable excess in serum levels of alanine and aspartate aminotransferase, creatinine and urea along with increased malondialdehyde activity in hepatic and renal tissues. In contrast a notable reduce in superoxide dismutase and glutathione levels has been reported. However, when administering thyme oil to poisoned rats with NiO-NPs, a clear attenuation of all studied parameters was observed. In conclude, thyme oil has defensive role against possible hepatorenal toxicity induced by nanoparticles.