Background: The adverse effects of a Western diet on obesity and diabetes among reproductive-aged women pose a significant threat to the cardiovascular health of their offspring. Given the crucial role of glutathione metabolism and glutathione-related antioxidant defense systems in cardiovascular diseases through scavenging ROS and maintaining redox homeostasis, further exploration of their specific influence is imperative to develop therapeutic strategies for cardiomyopathy induced by a maternal Western diet. Methods: We developed a prenatal maternal Western diet exposure model in C57/B6 mice to investigate cardiac morphology and function through histological analysis and echocardiography. RNA sequencing and analysis were utilized to elucidate the mechanisms underlying the impact of a maternal Western diet and N-acetylcysteine treatment on cardiomyopathy. Additionally, ELISAs, transmission electron microscopy, and flow cytometry were employed to assess the antioxidant defense system and mitochondrial ROS levels in progenitor cardiomyocytes. Results: N-acetylcysteine significantly mitigated cardiomyocyte hypertrophy, myocardial interstitial fibrosis, collagen type I accumulation, and left ventricular remodeling induced by a maternal Western diet, particularly in male offspring. Furthermore, N-acetylcysteine reversed the increase in apoptosis and the increase in the β/α-MyHC ratio in the myocardium of offspring that results from a maternal Western diet. RNA sequencing and GSEA revealed that the beneficial effects of N-acetylcysteine were linked to its ability to modulate oxidative phosphorylation pathways. Additionally, N-acetylcysteine treatment during pregnancy can markedly elevate glutathione levels, augment glutathione peroxidase (GPx) activity, and mitigate the accumulation of mitochondrial ROS caused by a maternal Western diet. Conclusions: N-acetylcysteine mitigated cardiomyopathy induced by a maternal Western diet by bolstering glutathione synthesis and enhancing GPx activity, thereby scavenging mitochondrial ROS and modulating oxidative phosphorylation pathways.