Introduction: Hepatitis B is a serious viral infection of the liver caused by the hepatitis B virus (HBV). This infection leads to inflammation of the liver, which can become chronic and result in liver cirrhosis and hepatocellular carcinoma. Objective: To determine the seroprevalence of HBsAg in patients at the Abéché University Hospital in Chad. Material and Methods: This was a prospective cross-sectional study conducted from April 1, 2022, to December 31, 2022, on a total of 845 patients aged 15 to 60 years seen in consultation at the Abéché University Hospital. HBsAg detection was performed using chromatography, and confirmation was carried out using the immunoassay method (ELISA). Results: The analysis showed that among the 845 patients tested, 112 were positive for HBsAg, representing an overall prevalence of 13.3% (112/845). Males represented 50.9% (430/845), while females represented 49.1% (415/845); the sex ratio was 1.03. The most affected age groups were 26–35 years (34.82% = 39/112), followed by 15–25 years (25.89% = 29/112). By occupation, farmers/livestock breeders were the most represented (61/112 = 54.46%), followed by homemakers (20.53% = 23/112). By marital status, married individuals were more affected (58.93% = 66/112) than single individuals (41.07% = 46/112). Conclusion: The seroprevalence of hepatitis B virus was relatively high in the population of Abéché, with more pronounced predominance among young people, married individuals, and particularly those working in agriculture and livestock farming. Combating the spread of this endemic infection in Chad requires strengthened strategies, including vaccination, targeted screening, and public awareness campaigns.