Background Despite recent advances in the treatment of hepatitis C, it is estimated that nearly 4 million Americans have a chronic form of the disease. Although research in lower-extremity arthroplasty suggests patients with hepatitis C are at risk for increased complications, including postoperative bleeding, acute postoperative infection, and general medical complications, no similar studies have investigated this question in patients undergoing total shoulder arthroplasty (TSA). Questions/purposes We asked whether there is an increased risk of postoperative complications after TSA among patients who have hepatitis C, and if so, what complications in particular seem more likely to occur in this population? Methods Patients who underwent TSA, including anatomic or reverse TSA, were identified in the PearlDiver database using ICD-9 procedure codes. This is a for-fee insurance patient-records database that contains more than 100 million individual patient records from 2005 to 2012. The Medicare data in the database are the complete 100% Medicare Standard Analytical File indexed to allow for patient tracking with time. Patients with hepatitis C who underwent shoulder arthroplasty then were identified using ICD-9 codes. Patients with hepatitis B coinfection or HIV were excluded. A control cohort of patients without hepatitis C who underwent TSA was created and matched to the study cohort based on age, sex, obesity, and diabetes mellitus. A total of 1466 patients with hepatitis C and 21,502 control patients were included. The two cohorts were statistically similar in terms of sex (53% females in study and control groups), age (nearly 1 . 2 of each cohort younger than 65 years), obesity (approximately 17% of each cohort were obese), diabetes (approximately 40% of each cohort had diabetes), and followup of each cohort occurred throughout the length of the database from 2005 to 2012. Postoperative complications were assessed using ICD-9 and Current Procedural Terminology codes and compared between cohorts.