Objective: Postoperative readmission rates can be used to assess hospital care quality. The rates of unplanned readmission within 30 days after spine surgery are variable in the literature, and no studies have evaluated such rates in a single Latin American center. This study aimed to assess the rate of unplanned hospital readmission within 30 days after a spine surgery at a single Brazilian institution and to identify possible risk factors. Methods: Patients who underwent spine surgery at a single private hospital between January 2018 and December 2020 were retrospectively analyzed, and those with unplanned readmissions within 30 days of discharge were identified. Risk factors were determined, and the reoperation rate was assessed. Results: 650 patients were included in the analysis, and 74 (11.28%) were readmitted within 30 days after surgery. Higher readmission rates were observed after vertebroplasty and surgeries involving spinal or bone tumors. The risk factors found in the series were older age, longer hospital stays, higher ASA scores, instrumented surgeries, diabetes mellitus, and surgeries involving primary or secondary spinal tumors. The most common causes of unplanned readmission were infection and pain. Of the readmissions, 28.37% required a return to the operating room. Conclusions: This study suggests infection and pain management were the most common causes of unplanned readmission after spine surgery. Strategies to improve perioperative and postoperative care are required to reduce unplanned readmissions. Level of Evidence III; Retrospective Comparative Study.