PURPOSE: To present a detailed analysis of postoperative clinical and radiographic outcomes of patients who underwent proximal thoracic pedicle subtraction osteotomy (PSO) for adult spinal deformity. METHODS: A retrospective chart review was performed on 19 patients who underwent proximal thoracic (T2-T4) PSO between January 2018 and December 2021. Baseline patient characteristics, complications and radiographic outcomes were collected. Radiographic outcomes including thoracic kyphosis correction, overall segment correction, and global sagittal balance correction were measured using preoperative and postoperative radiographs. RESULTS: 19 patients with an average age of 66.9 ± 8.3 years underwent thoracic PSO, with 94.7% (n = 18) being females, in the setting of revision surgery. The mean thoracic kyphosis correction was 20.4 ± 8.5°. Overall segmental correction had a mean of 16.2 ± 3.9°. Global sagittal balance correction was an average of 13.9 ± 23.2 mm (mm). The median hospital stay was 4.0 (IQR: 3.0) days with a median of 1.0 (IQR: 2.0) days in the intensive care unit. 36.8% (n = 7) of patients had a major complication within 30 days: proximal junction kyphosis (PJK) (2), neurologic deficits (2), pneumonia (1), cardiopulmonary (1), death (1). 47.4% (n = 9) of patients had a major complication within 2 years: PJK (5), neurologic deficits (2), wound dehiscence/infection (1), pneumonia (1), cardiopulmonary (1), death (2). Average follow up was 636 (range: 43-1320). CONCLUSION: While thoracic PSO can achieve successful radiographic and clinical outcomes, it is also associated with a high risk of potential major complications and mortality, such as instrumentation or junctional failure and neurologic deficits.