Purpose: The aim of this study was to investigate the relationship between pain duration and pain relief after epidural adhesiolysis. Materials and Methods: Patients with low back pain who underwent lumbar epidural adhesiolysis were enrolled. A clinically significant reduction in pain score was defined as a ≥30% reduction at 6-month follow-up evaluation. Variables were compared based on pain duration categories. Changes in pain scores and pain outcome were also compared. Logistic regression analysis was conducted to identify factors associated with pain relief after adhesiolysis. Results: A total of 169 patients, including 77 (45.6%) patients with a favorable pain outcome, were included for analysis. Patients with a pain duration ≥3 years reported lower baseline pain scores and showed more frequent severe central stenosis. Pain scores significantly decreased over time after the procedure except in patients with a pain duration ≥3 years. Most patients who experienced pain for ≥3 years showed poor pain relief (80.8%), unlike other pain duration categories (pain duration <3 months=48.1%, 3 months–1 year=51.8%, 1–3 years=48.6%). A pain duration ≥3 years and lower baseline pain score were independent factors associated with an unfavorable pain outcome. Conclusion Pain lasting ≥3 years prior to lumbar epidural adhesiolysis was associated with worse outcomes in terms of pain relief. Therefore, this intervention should be considered early before pain chronification in patients with low back pain.