AbstractHuman T‐lymphotropic virus 1/2 (HTLV‐1/2), hepatitis B virus (HBV), and hepatitis D virus (HDV) share transmission routes. Argentina shows low prevalence of HTLV‐1/2, HBV, and HDV infections; however, this situation may vary according to the geographic region and group studied. The aim of this study was to estimate the prevalence of HBV and HDV infections and detect both viral genotypes in HTLV‐1/2 individuals from Argentina. A total of 202 HTLV‐1/2 confirmed samples (blood donors [BD] and individuals with risk factors for HTLV‐1/2 [RF]) were tested for HBsAg and total anti‐HBc by enzyme‐linked immunosorbent assay. All reactive samples for some HBV markers were analyzed for HBV DNA characterization and HDV serological and molecular analysis. Total prevalence was 1.5% for HBsAg and 6.4% for anti‐HBc. Prevalence was 23.1% for anti‐HDV in all HBV‐reactive samples. No significant difference was observed for HBV and HDV prevalence within HTLV subtypes. The population study showed that prevalence of anti‐HBc was higher in the RF than in the BD population, with no significant differences between them. The HBsAg marker and anti‐HDV were only found in RF, showing significant differences when compared to BD. Regarding molecular detection, one sample amplified for HBV DNA and none for HDV RNA. HBV sequence was classified as subgenotype F1b. New and updated background on serological markers of HBV and HDV infection in patients with HTLV‐1/2 was provided.