Maternal obesity in pregnancy and lactation is linked to metabolic disturbances and neurodevelopmental problems in offspring, increasing the risk of psychiatric disorders in adulthood. We proposed that maternal N-acetyl cysteine (NAC) supplementation during lactation, a critical period for neurodevelopment, potentially protects offspring from developing cognitive impairment in adulthood. Fifteen young female ICR mice were randomly allocated to different experimental groups: high-fat diet (HFD
60.3% fat before mating, during pregnancy and lactation), HFD-NAC of 300 mg/kg/day during lactation, CD (high-fat diet before mating, during pregnancy, and regular chow control diet of 8.2% fat during lactation), CD-NAC of 300 mg/kg/day during lactation and control group consuming regular chow diet. The serum inflammatory markers of the offspring were evaluated post-weaning, while metabolic markers, microglial density, and cognitive performance were assessed in adulthood using the novel Object Recognition and Morris Water Maze tests. Our results demonstrate maternal obesity during gestation and lactation increased body weight, hepatic steatosis, and microglial cell density in the dentate gyrus (DG) and cortex. Furthermore, these offspring exhibited reduced spatial learning abilities in adulthood, regardless of sex. However, maternal NAC administration during lactation and maternal diet intervention significantly reduced brain microglial density and improved both male and female offspring metabolic profiles. More importantly, NAC supplementation during lactation, regardless of maternal diet, enhanced male offspring's learning ability in adulthood. Our findings indicate that administering NAC to obese mothers during the critical lactation period may offer protection against metabolic disturbances and cognitive deficits in adult offspring previously exposed to maternal obesity.