Objective: Double-level isthmic spondylolisthesis in the lumbar spine is rare. The authors report on 21 cases of double-level isthmic spondylolisthesis treated by posterior lumbar interbody fusion (PLIF) with cage.Patients and methods: Between 2005 and 2015, twenty-one patients with double-level isthmic spondylolisthesis who underwent posterior lumbar interbody fusion (PLIF) with cage were reviewed retrospectively. The VAS (Visual Analogue Scale) and JOA (Japanese Orthopedic Association) score were used to evaluate preoperative and postoperative clinical outcomes.Results: The back pain and sciatica decreased from 6.53 and 4.24 points preoperatively to 1.80 and 1.18 points on the VAS at final follow-up, respectively. The average JOA score improved from 13.4 ± 3.2 preoperative to 25.4 ± 1.5 (range, 17-28) points postoperative. The average recovery rate was 76.9%. The good and excellent rate was 85.7% (18/21). The fusion rate was 95.2% (20/21). Changes in disc height, degree of listhesis, whole lumbar lordosis, and sacral inclination following surgery were also observed.Conclusions: Our results suggest that PLIF with cage appears to be an appropriate technique for the treatment of double-level isthmic spondylolisthesis.