The occurrence of pancreatitis shortly after elective lumbar spine surgery in an adult is rare. We report a case of a 63-year-old female who developed, for the first time, acute pancreatitis within three days of elective lumbar (L) spine surgery that was performed for degenerative disk disease without significant deformity (i.e., no scoliosis or spondylolisthesis). The surgery was conducted using a lateral transpsoas approach and included interbody fusions at L3-L4 and L4-L5 levels and posterior instrumentation with pedicle screws and rods. Ten years prior, she had a cholecystectomy, and she was not diabetic or obese. She began experiencing significant nausea and malaise two days after that lumbar spine surgery, requiring hospitalization on the third postoperative day. Her pancreatitis became chronic, and a large pancreatic pseudocyst developed and persisted despite using an external drainage catheter for 52 days. At 126 days after the spinal surgery, an open Roux-en-Y pancreatic cystojejunostomy was performed to internally drain the cyst, which had enlarged to 19 cm. Significant pre-surgical risk factors for this first-time case of pancreatitis were not identified. The spine surgeon denied iatrogenic causes such as instrument plunging or complications associated with the use of a "lateral access retraction system," and surgical blood loss was only 50 ml during the elective lumbar spine surgery. However, during the lumbar spine surgery, hypotension occurred for 20 minutes (mean arterial pressure: 63-73 mmHg), which was associated with transient acute kidney injury. This might have contributed to the development of her pancreatitis because the pancreas is more sensitive to ischemia than the kidney. During the initial week after the onset of pancreatitis, her symptoms were mainly believed to be due to an acute postoperative infection. However, there was no growth in cultures from aspirations of the pleural effusion, retroperitoneal effusion, and deeper incision area. Despite extensive workup, the cause of the patient's pancreatitis was not determined. We report this case not only because of its rarity but also to help surgeons and other healthcare providers in the workup and management of similar situations.