Aspirin has been found to diminish hypertriglyceridemia and hyperglycemia in both obese rodents and patients with type 2 diabetes mellitus. We aimed to test whether low-dose aspirin can prevent obesity and the progression of non-alcoholic fatty liver disease (NAFLD) in high-risk subjects. We used offspring mice with maternal over-nutrition as a high-risk model of obesity and NAFLD. The offspring were given postnatal HF-diet and diethylnitrosamine (DEN) to induce obesity and NAFLD, and were treated with or without a low dose of aspirin for 12 weeks (ASP or CTL groups). Aspirin treatment reduced body weight gain, reversed glucose intolerance, and depressed hepatic lipid accumulation in female, but not in male mice. Female mice displayed re-sensitized insulin/Akt signaling and overactivated AMPK signaling, with enhanced level of hepatic PPAR-gamma, Glut4, and Glut2, while male mice only enhanced hepatic PPAR-alpha and PPAR-gamma levels. The female ASP mice had inhibited p44/42 MAPK activity and enhanced Pten expression, while male displayed activated p38 MAPK signaling. Furthermore, the female but not the male ASP mice reduced Wnt-signaling activity via both the epigenetic regulation of Apc expression and the post-transcriptional regulation of beta-catenin degradation. In summary, our study demonstrates a sex-associated effect of low-dose aspirin on obesity and NAFLD prevention in female but not in male mice.