For complex lumbar spinal stenosis, using of endoscopy technique may provide clear vision with less invasive dissection of paravertebral muscle. The objective of this study was to evaluate the feasibility and clinical efficacy of bilateral decompression and intervertebral fusion via unilateral fenestration for complex lumbar spinal stenosis using mobile microendoscopic discectomy (MMED) technique.A total of 61 patients with complex lumbar spinal stenosis (lumbar canal stenosis combined with degenerative spondylolisthesis, instability, and scoliosis) were treated with this procedure. Patients with isolated lumbar spinal stenosis or spondylolisthesis greater than grade II were excluded. The index levels included L4/5 in 52 patients, L5/S1 in 6 patients, L3-L5 in 2 patients and L4-S1 in 1 patient. The preoperative Oswestry Disability Index (ODI) score was 42.6 ± 10.2, lumbar visual analog scale (VAS) score was 6.1 ± 4.2, and leg VAS score was 7.1 ± 5.1. During the operation, ipsilateral enlarged fenestration was made using the MMED technique. The disc and cartilage endplate were thoroughly removed, and the contralateral ligamentum flavum and the inner layer of lamina were undercut to release the contralateral nerve root. The intervertebral space was released and prepared, followed by bone grafting and cage insertion. Percutaneous pedicle system was used for reduction and fixation. The operative time and blood loss were recorded, and patients were followed-up for at least 3 years (36-48 months, average 41 months) to evaluate the clinical efficacy.The procedure was successful in all patients, with no nerve injury or conversion to open operation. The mean operative time was 120 minutes (range, 100-180 minutes), with a mean blood loss of 100 mL (range, 50-200 mL). Postoperative x-ray and CT showed sufficient decompression and improvement of spinal alignment. At 3 years after surgery, the ODI scores, lumbar and leg VAS scores decreased from preoperative 42.6 ± 10.2, 6.1 ± 4.2, and 7.1 ± 5.1 to 8.6 ± 7.0, 1.8 ± 1.3, and 0.9 ± 0.6, respectively (P = .00 for each comparison). The clinical results were excellent in 36 cases, good in 23, and fair in 2, according to the MacNab scale.The procedure of bilateral decompression and intervertebral fusion via unilateral fenestration using the MMED technique can provide satisfactory clinical results for complex lumbar spinal stenosis.