Purpose There are limited and conflicting data regarding the impact of comorbid hepatitis C virus (HCV) infection on diabetic retinopathy (DR). This study sought to compare the prevalence and severity of DR among patients with diabetes mellitus (DM) with and without HCV. Patients and methods This was a retrospective, case–control study of patients with DM comparing 120 patients with comorbid HCV and 120 age-matched controls. DR prevalence and several measures of severity were compared between groups. Subgroup analyses were performed among HCV patients with cirrhosis, comorbid HIV, or history of treatment with interferon. Statistical analysis for between-group comparisons utilized both univariate and multivariate analyses. Results Cases and controls exhibited similar baseline characteristics: average hemoglobin A1c, DM duration, and age ( p >0.05). Among cases and controls, there was no difference in DR prevalence (35.8% versus 42.5%, respectively, p =0.29) or severity ( p >0.05). Within the HCV subgroup, DR severity was reduced in patients with HIV or cirrhosis. However, multivariate analysis identified reduced DM duration in these subgroups as the primary contributor to lesser DR severity, rather than HIV or cirrhosis. Conclusion In this study, comorbid HCV did not modulate the prevalence or severity of DR among patients with DM. These findings may inform clinical monitoring among HCV-positive diabetics undergoing ophthalmic evaluation.