Isthmic spondylolisthesis, which is demonstrated in 4%-6% of the general population, is one of the most common types of spondylolisthesis. However, double-level isthmic spondylolisthesis is extremely rare. Only a few reports have examined the outcomes of surgical treatment of double-level spondylolisthesis. The authors present an unusual case of double-level isthmic spondylolisthesis of the lumbar spine. The patient had low-back pain for 20 years and did not respond to conservative treatment. Radiographs revealed bilateral pars defects at L-4 and L-5. Grade 2 isthmic spondylolisthesis was present, both at L4-5 and at L5-S1. The patient underwent decompression, reduction, and posterior lumbar interbody fusion with autogenous bone chips from posterior decompression. At follow-up after 12 months, the patient was free of pain, slippage was corrected, and fusion was achieved. Posterior lumbar interbody fusion with posterior instrumentation and reduction may yield good functional short-term results for double-level spondylolisthesis.