BACKGROUND There is growing policy interest in reducing the length of stay (LOS) after discretionary orthopedic surgery but few data to guide improvement efforts. We characterized the primary reasons and predisposing factors associated with extended LOS after elective total shoulder arthroplasty. METHODS We retrospectively identified 415 patients undergoing elective primary total shoulder arthroplasty between 2016 and 2017. Extended LOS was defined as a stay greater than the 75th percentile. Medical records were manually reviewed to ascertain the primary reason for extended LOS. Multivariable logistic regression modeling was used to determine preoperative characteristics associated with prolonged hospitalization. RESULTS The most common reason for extended LOS was pain (41%), followed by medical problems (39%), limited social support (18%), and blood transfusions (2%). Only 41% of patients with delayed discharges had documented adverse events (any medical or surgical problem), all of which were minor. The top 4 medical issues were transient hypoxemia (42%), nausea and/or vomiting (13%), electrolyte abnormalities (12%), and altered mental status (10%). In decreasing order of magnitude, the predictors of prolonged LOS were greater number of self-reported allergies, female sex, unmarried patient, diabetes, lower American Shoulder and Elbow Surgeons score, depression, reverse shoulder arthroplasty, and American Society of Anesthesiologists score of 3 or greater. Operative time did not correlate with LOS. CONCLUSIONS Prolonged hospitalizations after shoulder arthroplasty are commonly related to pain and limited social support. Sociodemographic and psychological factors seem to have more influence than patient infirmity and technical issues. These findings support a comprehensive approach to care with attention to the physical, mental, and social determinants of health.