Most patients with hepatitis C virus (HCV) infection perceive some degree of disease-related stigma. Misunderstandings about diseases may contribute to disease-related stigma. The objective of this study was to evaluate patient-level knowledge about HCV infection transmission and natural history and its association with HCV-related stigma among HCV-infected patients. We conducted a cross-sectional survey study among 265 patients with HCV in Philadelphia using the HCV Stigma Scale and the National Health and Nutrition Examination Survey (NHANES) Hepatitis C Follow-up Survey (2001-2008). The association between HCV knowledge and HCV-related stigma was evaluated via linear regression. Overall knowledge about HCV transmission and natural history was high, with >80% of participants answering ≥9 of 11 items correctly (median number of correct responses, 9 [82%]), HCV-related knowledge was similar between HIV/HCV-coinfected and HCV-monoinfected participants (p = 0.30). A higher level of HCV-related knowledge was associated with greater perceived HCV-related stigma (β, 2.34 ([95% CI, 0.51-4.17]; p = 0.013). Results were similar after adjusting for age, race, ethnicity, HIV status, education level, stage of HCV management, time since diagnosis, and history of injection drug use. In this study, increased HCV-related knowledge was associated with greater perceptions of HCV stigma. Clinicians may consider allotting time to address common misconceptions about HCV when educating patients about HCV infection, which may counterbalance the stigmatizing impact of greater HCV-related knowledge.