Background: The objective was to assess social functioning and its association with treatment intent, specialist assessment and treatment uptake for hepatitis C virus (HCV) infection among people with a history of injecting drug use. Methods: ETHOS is a prospective observational cohort evaluating the provision of HCV assessment and treatment among people with chronic HCV and a history of injecting drug use, recruited from nine community health centres and opioid substitution treatment clinics (NSW, Australia). Social functioning was assessed using a short form of the Opioid Treatment Index social functioning scale. Those classified in the highest quartile (score >6) were considered having lower social functioning. Analyses were performed using logistic regression. Results: Among 415 participants (mean age 41 years, 71% male), 24% were considered having lower social functioning, 70% had early HCV treatment intent (intention to be treated in the next 12 months), 53% were assessed by a specialist and 27% initiated treatment. Lower social functioning was independently associated with unemployment, unstable housing, recent injecting drug use and moderate to extremely severe symptoms of depression, anxiety and stress. Lower social functioning was independently associated with reduced early HCV treatment intent (aOR 0.51, 95% CI 0.30-0.84) and lower specialist assessment (aOR 0.48, 95% CI 0.29-0.79), but not HCV treatment uptake (aOR 0.76, 95% CI 0.40-1.43). Living with someone was independently associated with HCV treatment uptake (with someone and children: aOR 2.28, 95% CI 1.01-5.14; with someone and no children: aOR 2.36, 95% CI 1.30-4.31), but not early HCV treatment intent or specialist assessment. Conclusions: This study highlights the need for the development and implementation of strategies targeting people who inject drugs with lower social functioning to enhance HCV treatment intent and specialist assessment. Further, strategies to enhance social support may play a role in increasing HCV treatment uptake.