Background: Lumbar degenerative spondylolisthesis (LDS) is a degenerative slippage of the lumbar vertebrae. We aimed to evaluate the surgical outcome of degenerative spondylolisthesis with neural decompression, pedicular screw fixation, reduction, and posterolateral fusion.Methods: This before-after study was carried out on 45 patients (37 female and 8 male) with LDS operated from August 2008 to January 2011. The patients’ pain and disability were assessed by visual analogue scale (VAS) and Oswestry disability index (ODI) questionnaire. In surgery, we applied distraction force to facilitate slip reduction. All the intra- and postoperative complications were recorded. The paired t-test and Pearson correlation coefficient were used for statistical analysis.Results: The mean age of patients and mean follow-up period were 58.3±3.5 years and 31.2±4.8 months, respectively. The mean slip correction rate was 52.2% with a mean correction loss of 4.8%. Preoperative VAS and ODI improved from 8.8 and 71.6 to postoperative 2.1 and 28.7, respectively. Clinical improvement was more prominent in more reduced patients, but Pearson coefficient could not find a significant correlation.Conclusion: Although spinal decompression with fusion and posterior instrumentation in surgical treatment of the patients with LDS result in satisfactory outcome, vertebral reduction cannot significantly enhance the clinical improvement.