Background: The number of elderly patients undergoing adult spinal deformity (ASD) surgery has increased with the advent of new techniques and more nuanced understanding of global malalignment as patients age. The relationship between inpatient physical activity after ASD surgery and postoperative complications in elderly patients has not been reported; thus, we sought to investigate this relationship.Methods: We performed a medical record review of 185 ASD patients older than 65 years (age: 71.5 ± 4.7; body mass index: 30.0 ± 6.1, American Society of Anesthesiologists: 2.7 ± 0.5, and levels fused: 10.5 ± 3.4). We derived the number of feet walked over the first 3 days after surgery from physical therapy documentation and evaluated for association with 90-day perioperative complications. Patients who sustained an incidental durotomy were excluded from the study.Results: The 185 patients were divided into groups based on whether they were among the 50th percentile for number of feet walked (62 ft). Walking less than 62 ft after ASD surgery was associated with higher incidence of postoperative complications (54.3%, P = 0.05), cardiac complications (34.8%, P = 0.03), pulmonary complications (21.7%, P = 0.01), and ileus (15.2%, P = 0.03). Patients who developed any postoperative complication (106 ± 172 vs 211 ± 279 ft, P = 0.001), ileus (26 ± 49 vs 174 ± 248 ft, P = 0.001), deep venous thrombosis (23 ± 30 vs 171 ± 247 ft, P = 0.001), and cardiac complications (58 ± 94 vs 192 ± 261 ft) walked less than patients who did not.Conclusion: Elderly patients who walked less than 62 ft in the first 3 days after ASD surgery have a higher rate of postoperative complications, specifically pulmonary and ileus compared with those patients who walked more. Steps walked after ASD surgery may be a helpful and practical addition to the surgeon's armamentarium for monitoring the recovery of their patients.Clinical Relevence: Monitoring the steps walked by patients after ASD surgery can be a practical and useful tool for surgeons to track and improve their patients' recovery.Level of Evidence: 3.