Introduction: The aging population has led to an increasing volume of major surgeries among older adults. Age-related declines in physiological and functional capacity may contribute to worse postoperative outcomes. We assessed the impact of postoperative geriatric syndrome (GS) on days at home (DAH) after discharge, mortality and complications. Methods: Medicare beneficiaries who underwent a major surgical procedure [coronary artery bypass grafting (CABG), pneumonectomy, abdominal aortic aneurysm (AAA) repair, pancreatectomy, colectomy] between 2016 and 2021 were identified. GS was defined as diagnosis of delirium, falls, fractures, pressure ulcers, failure to thrive, dehydration, incontinence, depression, or malnutrition during index hospitalization. Primary outcomes included DAH within 90 days (DAH-90) and 1-year overall survival. Results: Among 780,337 patients (CABG: 30.2%, pneumonectomy: 9.0%, AAA: 24.6%, pancreatectomy: 1.8%, colectomy: 34.3%), 10.9% (n=84,760) developed new-onset GS. Independent predictors of GS included age (OR 1.03, 95%CI 1.03-1.03), Charlson Comorbidity Index (OR 1.61, 95%CI 1.58-1.64), emergency procedures (OR 1.57, 95%CI 1.55-1.60), and procedure type (ref: AAA; pancreatectomy: OR 3.86, 95%CI 3.67-4.07). New-onset GS was associated with higher risk of 30-day complications (HR 3.53; 95% CI 3.48–3.60), prolonged hospitalization (HR 5.37; 95% CI 5.28–5.45), and non-home discharge (HR 3.90; 95% CI 3.83–3.98). Patients with GS had fewer DAH-90 (66 [IQR 21–79] vs. 82.5 [IQR 74–86], p<0.001), with the lowest DAH-90 (52 [IQR 0-73]) among patients with GS and concurrent postoperative complications. New-onset GS was also associated with higher risk of 1-year mortality (HR 2.32; 95% CI 2.29–2.36). Conclusions: New-onset GS after major surgery was associated with adverse short- and long-term outcomes among older adults. These findings emphasize the importance of optimizing perioperative care in this population.