(1) BACKGROUND: There are limited data regarding human immunodeficiency virus (HIV) prevalence among hepatitis B virus (HBV) or hepatitis C virus (HCV) infected individuals. The aim of this cross-sectional study is to determine the prevalence of HBV and HCV infection among HIV individuals; (2) METHODS: A total of 409 patients (126 HBV+ and 283 HCV+) referred to the Brazilian Reference Laboratory for Viral Hepatitis from 2010 to 2013 donated serum samples. Anti-HIV, HBsAg, anti-HBc, anti-HBs, anti-HBcIgM, anti-HBe, HBeAg, and anti-HCV antibodies were measured, and anti-HCV positive samples were tested for viral RNA and genotype; (3) RESULTS: The anti-HIV antibody prevalence was 10.31% and 4.59% among HBV+ and HCV+ patients, respectively. The HCV mean (SD) viral load was log 5.14 ± 1.64 IU/mL, and genotype I was most prevalent (163/283). Anti-HBs and anti-HBc were detected in 40% and 26% of HCV+ individuals, respectively. Among the HBV+ population, the presence of anti-HIV antibodies was associated with male gender, marital status (married), tattoo, sexual orientation, sexual practices (oral sex and anal sex), history of sexually transmitted diseases (STDs), history of viral hepatitis treatment, and a sexual partner with hepatitis or HIV. For the HCV+ group, the presence of anti-HIV antibodies was associated with female gender, marital status (married), anal intercourse, previous history of STDs, and number of sexual partners; (4) CONCLUSION: A high prevalence of anti-HIV antibodies was found among individuals with HBV and HCV, showing the importance of education programmes towards HIV infection among HBV- and HCV-infected individuals.