Objectives: To examine increased notifications of hepatitis C virus (HCV) in men who have sex with men (MSM) infected with HIV in Victoria, and evaluate HCV transmission risk factors other than injecting drug use. Design, setting and participants: Case series through retrospective review of all HCV cases in Victoria from 1 April 2010 to 30 June 2011, with clinical and laboratory data examined in likely MSM to identify a co-infected cohort. Patients with newly acquired HCV with HIV co-infection were invited to complete a questionnaire exploring novel risk factors for HCV transmission (non-injecting drug use, sexual practices with increased likelihood of trauma, and presence of genital ulcers). Sequencing was performed to determine the local molecular epidemiology of HCV co-infection. Main outcome measures: Demographics of newly co-infected MSM, traditional versus novel risk factors for HCV acquisition, prior knowledge of potential for sexual transmission of HCV, and association between viral sequences. Results: Thirty-one patients with HIV were identified from 3365 notifications of hepatitis C. The median age was 42 years, and median time from HIV to HCV diagnosis was 22 months. Most patients were asymptomatic, with abnormal liver function tests prompting HCV testing. Interviews with 14 patients identified a high prevalence of novel risk factors and limited knowledge of HCV risk. Two clusters of matching viral sequences were identified. Conclusions: Novel HCV transmission routes have emerged in Victoria. These data reinforce the need for targeted testing and prevention strategies among HIV-infected MSM.