Posterior transpedicular instrumentation is commonly used for the treatment of spondylolisthesis. Migration of the lumbar rod to posterior sacral region is extremely unusual. In this report, a 73-year-old-female patient with the migration of lumbar rod to posterior sacral region is presented. She had been placed a posterior trans-pedicular screw-rod instrumentation system for L4-L5 spondylolisthesis four years ago. The anteroposterior and lateral lumbosacral roentgenograms revealed that left-sided rod released completely from the fixation points and migrated down caudally to the sacral area. This case report emphasizes the importance of careful surgical technique and long-term follow up for the cases that have undergone spinal instrumentation surgery.