Accumulating evidence suggests that oxidative stress induced mechanisms are believed to be associated with the pathophysiology of autism. In this study, we recruited 19 Omani autistic children with age-matched controls to analyze their plasma and serum redox status and the levels of ATP, NAD+ and NADH using well established spectrophotometric assays. A significant decrease was observed in the levels of plasma total antioxidants (TA), reduced glutathione (GSH), superoxide and catalase activity in Omani autistic children as compared to their age-matched controls. In contrary, the level of plasma glutathione peroxidase (GSH-Px) was significantly increased in autistic children. Reduced serum NAD+ and ATP levels and lower NAD+:NADH ratio were observedin patients with autism compared to controls. Finally, a significant inverse correlation was observed between plasma GSH, SOD, catalase activity, and serum NAD+ and ATP levels, and autism severity using Childhood Autism Rating Scale (CARS) scores. The levels of plasma GSH-Px and serum NADH correlated strongly with autism severity whilst no significant correlation was observed for plasma TOur data suggests that increased vulnerability to oxidative stress in autism may occur as a consequence of alterations in antioxidant enzymes leading to mitochondrial dysfunction.