PURPOSE: Little is known about metabolic syndrome in the peri-operative shoulder surgery setting. We sought to determine the prevalence of metabolic syndrome in patients undergoing shoulder arthroplasty, and to characterize its relationship with in-hospital adverse events, prolonged length of stay, and non-routine disposition. METHODS: Using discharge records from the 2002-2011 Nationwide Inpatient Sample, temporal trends were assessed and multivariable logistic regression modeling was used to measure the association of metabolic syndrome with peri-operative outcomes. RESULTS: The prevalence of metabolic syndrome increased by 257 % from 2002 to 2011 (4.2 to 15.0 %). Metabolic syndrome was associated with increased aggregate morbidity (OR 1.34, 95 % CI 1.30-1.38), including acute renal failure (OR 1.51, 95 % CI 1.41-1.63), surgical site infection (OR 1.41, 95 % CI 1.16-1.71), myocardial infarction (OR 1.32, 95 % CI 1.12-1.55), acute posthemorrhagic anemia (OR 1.30, 95 % CI 1.26-1.34), and pulmonary embolism (OR 1.27, 95 % CI 1.06-1.52). It was also associated with prolonged hospital stay (OR 1.13, 95 % CI 1.10-1.16), non-homebound discharge (OR 1.29, 95 % CI 1.26-1.32), and increased blood transfusion use (OR 1.09, 95 % CI 1.06-1.13). CONCLUSIONS: Metabolic syndrome is increasing rapidly among shoulder arthroplasty patients and is associated with considerable peri-operative morbidity and resource utilization. Greater awareness of metabolic syndrome and its health consequences may contribute to improvements in the peri-operative management of shoulder arthroplasty patients.