The biochemical, oxidative DNA damage, and the histological alterations associated with thiamethoxam (MX) exposure, a second-generation neonicotinoid broadly used in Egyptian agriculture, were assessed. Also, the role of N- acetylcysteine (NAC), (150 mg/kg/day) on the adverse effect of MX was investigated. Rats were orally preserved with a sub-lethal dose (1/50 LD50) of MX at 31.26 mg/kg/day, five doses/week for 28 days. The MX exposure resulted in a significant decrease in rats' body weight, protein concentration of both serum and urine, sera superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities compared to control. In addition increase in sera creatinine, urea, bilirubin, alkaline phosphatase (ALP), and malondialdehyde (MDA) levels were observed. While the assessment of DNA damage revealed significant elevation in 8-hydroxy-2'-deoxyguanosine (8-OH-2DG) levels in both serum (428.9%) and urine (234.6 %) samples. The present findings were supported by microscopic observation of liver and kidney tissues. Evidently, thiamethoxam can damage liver and kidney functions impaired the DNA, and caused histoarchitecture lesions in rats at the tested sublethal dose. In addition, NAC supplementation significantly attenuated the MX DNA damaging effect to be 49.1% and 50.18% for serum and urine, respectively compared to the control which reflects its protective properties against MX-induced hepatic-nephrotoxicity.