Objective: To determine frequency of thyroid dysfunction among patients of chronic hepatitis C receiving combined pegylated interferon alpha and ribavirin therapy. Study Design: Cross sectional study. Place and Duration of Study: Department of Medicine, Military Hospital Rawalpindi, from Jan to Jul 2017. Methodology: One hundred and twenty patients, aged 18–60 years from both genders, with established hepatitis C were included; while the patients with decompensated liver disease, previous antiviral treatment, pre-existing thyroid, autoimmune or severe cardiopulmonary disease and on immuno-suppressants or steroids were excluded. After formal informed consent, they were prescribed 24 weeks pegylated interferon alpha-2 (3 million units subcutaneously thrice weekly) and oral ribavirin (1000–1200 mg daily) therapy. After 12 weeks, serum thyroid stimulating hormone, free thyroxine and triiodothyronine levels were determined by chemiluminescence technique. Results: Out of 120 patients, 100 (83.33%) were males and 20 (16.67%) were females with male to female ratio of 5:1. Mean thyroid stimulating hormone levels at baseline and 12 weeks were 2.86 ± 1.03uiu/ml and 2.16 ± 0.79 uiu/ml respectively. Mean triiodothyronine levels at baseline and 12 weeks were 3.27 ± 1.31pg/ml and 2.69 ± 1.01 pg/ml respectively. Mean thyroxine levels at baseline and 12 weeks were 1.26 ± 0.38 pg/ml and 1.07 ± 0.53 pg/ml respectively. Frequency of thyroid dysfunction was found in 40 (33.33%) patients. Conclusion: Frequency of thyroid dysfunction among hepatitis C patients receiving combined pegylated interferon alpha and ribavirin therapy is quite high.