Autoantibodies are commonly detected in chronic hepatitis C (HCV) but their significance remains uncertain. We assessed the prevalence of anti-nuclear (ANA) and anti-smooth muscle (ASM) antibodies within a cohort of 963 treatment-naïve HCV patients. We also assessed for differences between autoantibody-positive and autoantibody-negative patients in demographics, markers of disease activity and response to anti-viral treatment. One hundred and seventy-two patients (17.9%) had at least one autoantibody, of which were 104 (10.8%) ASM, 54 (5.6%) ANA and 14 (1.5%) positive for both. Autoantibody-positive patients were older (43 vs 39 years, P = 0.001) caused by an age-related increase in ANA (but not ASM). There were no differences in gender, alcohol intake, ethnicity or viral genotype. The presence of autoantibodies, and specifically ASM, was associated with an increase in interface hepatitis score amongst men (1.1 vs 0.8, P = 0.005) but no difference in other necroinflammatory measures, liver function tests or immunoglobulins (Ig). There was no difference in initial fibrosis stage or rate of fibrosis progression. Autoantibodies did not affect response to anti-viral treatment. We conclude that autoantibodies are frequent in HCV infection. Anti-nuclear antibodies increase with age, whereas ASM antibodies are associated with interface hepatitis in men. Neither autoantibody carries increased risk of fibrosis progression or failure of therapy.