Purpose Gastroesophageal reflux disease (GERD) is reported as one of the symptoms of adult spinal deformity (ASD). Little is known about the mid-to long-term improvement in GERD symptoms after ASD surgery. Therefore, this retrospective study from prospectively collected database aimed to investigate GERD symptoms in patients for a minimum of 2 years after ASD corrective surgery. Methods Records from 230 patients (mean age: 64 years) who underwent ASD surgery were examined using the frequency scale for the symptoms of GERD (FSSG) questionnaires for the diagnosis of GERD. FSSG scores and radiographic parameters were investigated preoperatively and postoperatively at 6 months and 1, 2, and 5 years. Results In total, 90 (39%) patients were preoperatively diagnosed with GERD defined by FSSG score ≥ 8 points. Radiographic results showed that the corrective surgeries improved local and global alignments. In the GERD patients, preoperative FSSG scores (16.1 ± 7.3 points) significantly improved to 7.7 ± 7.4 points within 6 months postoperatively (p < 0.001), and postoperative FSSG scores maintained at 1 year (9.9 ± 8.2 points, p = 0.061), 2 years (9.7 ± 8.2 points, p = 0.086), and 5 years (9.4 ± 8.0 points, p = 0.177). Among the GERD group, 62 patients (69%; improvement cases) showed improvement in GERD symptoms defined by FSSG score < 8 points within 6 months postoperatively. Conclusions Among ASD patients, 39% were diagnosed with GERD. In 69% of these patients, GERD symptoms improved within 6 months of corrective surgery and maintained up to 5 years postoperatively.