Drug-resistance mutations (DRM) of HBV in HIV coinfected patients undergoing HAART are complex and incompletely understood. We aim to determine the prevalence of HBV, HBV genotypes, and DRM in a cohort of HIV-infected patients in the northeast region of Colombia. This was a cross-sectional study in HIV patients between January 2010 and July 2011. Virological, immunological and HAART were collected from clinical records. An in-house nested PCR of HBV pol gene was used to identify coinfections, genotypes, DRM and HBV s antigen (HBsAg) escape mutants. Out of 275 subjects, 11.6% were identified as HIV-HBV coinfections from which 3.3% were HBsAg positive. All HBV sequences (n=23) belonged to genotype F3. Among HIV/HBV coinfections, 71.9% had CD4+ T cell counts above 200 cells/mm ³ and 37.5% undetectable HIV viral loads. DRM rtL80I, rtL180M, and rtM204V, which confer resistance to Lamivudine, were found in all HBV isolates. Also, a rt236Y unknown mutation to Tenofovir was identified and HBsAg escape mutations were not observed. Most patients received first-generation HBV antiviral therapy with a low genetic barrier to resistance. In Summary, these findings highlight the importance of molecular HBV screening and new guidelines to overcome DRM and prevent HBV-related liver diseases.