Background: In recent years there has been an increase in the incidence of acute hepatitis C virus (HCV) in men who have sex with men (MSM). The aim of the present study was to examine the prevalence of HIV/HCV co-infection among MSM in Sydney, and to compare sexual and drug use risk practices of HIV/HCV co-infected MSM with HIV and HCV mono-infected MSM. Methods: Data were collected from gay and other homosexually active men as part of the ongoing Gay Community Periodic Surveys (GCPS). The analysis herein presents findings from the Sydney GCPS in August 2011, which collected data on HCV for the first time. The survey was completed by 2009 respondents. Results: Three per cent of respondents self-reported being HCV positive (representing 9.0% of HIV-positive men and 1.9% of HIV-negative men). Overall, 1.2% of respondents reported being HIV/HCV co-infected. HIV/HCV co-infected men were more likely than HCV or HIV mono-infected men to report several sexual and drug use practices that may increase the risk of blood-borne virus transmission. Conclusions: Consistent with other research, we found a higher prevalence of HCV among HIV-positive than HIV-negative men. Several risk practices were more commonly reported among HIV/HCV co-infected men. These findings, and the increasing incidence of HCV in MSM, reinforce the need for routine HCV screening in this population.