Background: Hepatitis C virus (HCV) infection is endemic in Mongolia, with reported prevalence of HCV antibody (anti-HCV) positivity of 11%–16% in the adult population. Healthcare-related risk factors associated with development of acute HCV infection have not been evaluated in this population. Methods:We conducted a prospective, matched case-control study to identify risk factors associated with acute HCV infection in Ulaanbaatar, Mongolia. Cases were aged 18 years with discrete onset of symptoms consistent with acute viral hepatitis as well as jaundice or elevated serum alanine aminotransferase (ALT) levels who were admitted to the National Center for Communicable Diseases during January–October, 2019. Cases were both anti-HCV and HCV RNA positive and tested negative for acute hepatitis A, B, and E. Controls were randomly selected from the Population and Household Database, a national registry of all citizens, and were matched by age and gender. Data collection covered healthcare-associated and other risk factors in the 6 months before symptom onset (cases) or interview date (controls). Adjusted measures of association comparing cases and their matched controls were obtained using a multivariate conditional logistic regression model. Results: We enrolled 35 case patients and 104 controls. Median age of all participants was 44 (range, 23–63) years and 19% (27 of 139) were men. All case patients reported jaundice and loss of appetite; most cases reported nausea, malaise, and abdominal pain (97%, 91%, and 83%, respectively). The median ALT level among case patients was 1,185 IU/L (range, 212–3,349). Case patients were more likely than controls to have been admitted as inpatients (matched odds ratio [mOR], 4.3; 95% CI, 1.5–11.9), to have visited an outpatient clinic (mOR, 3.6; 95% CI, 1.3–10.2), to have had phlebotomy (mOR, 3.3; 95% CI, 1.5–7.5) or endoscopy (mOR, 10.7; 95% CI, 2.2–51.2) as an outpatient procedure, and to have received an injection outside of healthcare settings (mOR, 2.2; 95% CI, 1.0–5.1). Cases were also more likely to have lived in a yurt (mOR, 2.3; 95% CI, 1.0–5.0) and to have lived with persons diagnosed with HCV infection (mOR, 3.0; 95% CI, 1.1–7.9). In a multivariate model, only outpatient endoscopy (adjusted OR, 10.8; 95% CI, 1.7–69.6) was significantly associated with case status. Conclusions: This is the first study to evaluate risk factors for acute HCV infection among adults in Ulaanbaatar, Mongolia. Outpatient endoscopy was associated with new HCV infections in this population; evaluation of gaps in infection control practices at settings providing these services are needed to prevent transmission of communicable diseases, including hepatitis C.