Relatively little is known about the role of hepatitis B virus (HBV) genotype G (HBV/G) in patients co-infected with human immunodeficiency virus (HIV) and HBV. This study examined the prevalence and association of HBV/G to liver fibrosis in co-infected patients. HBV genotypes were determined by direct sequencing of the HBV surface gene or Trugene® HBV 1.0 assay in 133 patients infected with HIV/HBV. Quantitative testing of HBV-DNA, HBeAg, and anti-HBe were performed using the Versant® HBV 3.0 (for DNA) and the ADVIA®Centaur assay. The non-invasive biomarkers Fib-4 and APRI were used to assess fibrosis stage. Genotype A was present in 103/133 (77%) of the cohort, genotype G in 18/133 (14%) with genotypes D in 8/133, (6%), F 2/133 (1.5%), and H 2/133 (1.5%). Genotype G was associated with hepatitis B e antigen-positivity and high HBV-DNA levels. Additionally, HBV/G (OR 8.25, 95% CI 2.3–29.6, P = 0.0012) was associated with advanced fibrosis score using Fib-4, whereas, being black was not (OR 0.19, 95% CI 0.05–0.07, P = 0.01). HBV/G in this population exhibited a different phenotype than expected for pure G genotypes raising the question of recombination or mixed infections. The frequent finding of HBV/G in co-infected patients and its association with more advanced fibrosis, suggests that this genotype leads to more rapid liver disease progression. Further studies are needed to understand why this genotype occurs more frequently and what impact it has on liver disease progression in patients with HBV/HIV. J. Med. Virol. 83:1551–1558, 2011. © 2011 Wiley-Liss, Inc.