Objective: Identify risk factors for 30-day reoperation and readmission after parathyroidectomy for primary hyperparathyroidism. Study Design: Retrospective analysis of the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database from 2012 through 2014. Subjects and Methods: Patients undergoing parathyroidectomy and parathyroid reexploration for primary hyperparathyroidism. Univariate and multivariate analyses were conducted to determine risk factors for reoperation and readmission. Results: Of the 9439 patients who underwent parathyroidectomy, 72 patients underwent 1 reoperation in the first 30 days after surgery, and 8 patients underwent 2 reoperations. The most common reasons were hematoma (25%) and persistent hyperparathyroidism (15.9%). Risk factors included smoking (odds ratio [OR], 1.86; 95% confidence interval [CI], 0.97-3.31), insulin-dependent diabetes (OR, 2.38; 95% CI, 1.02-4.86), and history of bleeding disorder (OR, 3.95; 95% CI, 1.48-8.79). In total, 182 (1.9%) patients were readmitted within 30 days of surgery; the most common cause was hypocalcemia (17.0%). Risk factors included operative time (hours) (OR, 1.3; 95% CI, 1.1-1.5), insulin-dependent diabetes mellitus (OR, 2.01; 95% CI, 1.2-3.3), dyspnea with moderate exertion (OR, 5.77; 95% CI, 0.86-14.67), and age (decade) (OR, 1.16; 95% CI, 1.02-1.32). Patients undergoing outpatient surgery were less likely to be readmitted (OR, 0.49; 95% CI, 0.35-0.69) or undergo reoperation (OR, 0.44; 95% CI, 0.27-0.73). Conclusions: Thirty-day reoperation rate after parathyroidectomy was low and most commonly occurred due to hematoma. Risk factors for readmission were multifactorial and associated with perioperative factors, patient factors, and medical comorbidities. Preoperative counseling for patients at increased risk of readmission and reoperation may decrease these rates.