We conducted a study to characterize the risk factors for extended length of stay (LOS) and readmission after primary total shoulder arthroplasty (TSA). Patients who were 60 years or older and underwent TSA between 2011 and 2012 were identified from the American College of Surgeons National Surgical Quality Improvement Program database. Bivariate and multivariate analyses were used to test patient characteristics for association with extended LOS and readmission within 30 days. Extended LOS was defined as LOS of more than 3 days (90th percentile LOS). Of the 1505 TSA patients identified, 49 (3.3%) were readmitted. Multivariate analysis revealed that extended LOS was independently associated with age 70 years or older and history of diabetes. Readmission was independently associated with history of heart disease and history of hypertension. The identified risk factors may be useful for preoperative discussions, surgical decision-making, and postoperative planning for THA patients.