?Background. Hepatocellular carcinoma (HCC) is a major public health concern in Mexico being a leading cause of cancer mortality in individuals over 60 years old. Aflatoxin B1 (AFB1), one of the most potent hepatic carcinogens, frequently contaminates staple foods such as maize and is an important risk factor for HCC. Objectives. This study aimed to assess the role of AFB1 exposure in five Mexican states with high HCC mortality and exposure prevalence to AFB1—Campeche, Chiapas, Tamaulipas, Veracruz, and Yucatán—through a risk assessment approach. Methods. Using serum AFB1-lysine (AFB1-lys) biomarker data from 936 participants selected using probabilistic multistage stratified cluster sampling from the 2018 National Health and Nutrition Survey (ENSANUT), we calculated the following, overall and by state: 1. Exposure: as the estimated daily intake (EDI) of AFB1 (ng/kg/day), 2. Risk, as: a) Margin of exposure (MOE): which is the unitless ratio of the no-observed-adverse-effect level of AFB1 intake (benchmark dose expressed in ng/kg/day) to the EDI of AFB1, b) Expected number of HCC cases attributed to AFB1. We first calculated the local cancer slope factor (CSF)— which expresses the increased risk for each unit of exposure (ng/kg/day)-1— adjusting for hepatitis B virus prevalence in the population, given the synergistic effect of these risk factors, to account for positive and negative individuals. Then, we estimated the unitless cancer risk (EDI x CSF) and multiplied it by the population at risk to get the expected number of cases. Results. Overall, the average EDI for AFB1 was 14.9 ng/kg/day and the 95th percentile of exposure reached 58.1 ng/kg/day. The overall MOE for the mean (25) and the 95th exposure percentile (6) were far below the safety buffer for genotoxic and carcinogenic substances (10,000). The highest HCC risk expressed as MOE (therefore least separation between the EDI and the effect threshold) was observed in Veracruz (29), followed by Chiapas (42), Yucatan (55), Campeche (75), and Tamaulipas (181). Using our estimated central and upper bound CSF (0.018/ng/kg/day and 0.052/ng/kg/day, we estimate that AFB1 exposure could be responsible for 27 to 279 HCC cases annually in the states studied, with over 60% of them occurring in Veracruz due to high exposure levels and population size. Conclusions/Implications for practice or policy. The low MOEs obtained suggest substantial health risks for HCC attributed to AFB1 overall and in each state studied. The geographic concentration of cases highlights the importance of targeted interventions and strengthened food safety and public health strategies. This study underscores the preventable nature of AFB1-related HCC by providing critical risk data for previously unexamined regions and enhances exposure estimation accuracy and population representativeness.