Grynfeltt–Lesshaft hernia is a rare type of posterolateral abdominal wall hernia that may be either congenital or acquired. Only a few cases have been reported following surgical procedures. The risk of herniation increases after surgeries involving this region due to the weakening of the musculofascial structures, particularly in operations involving the thoracolumbar junction. Proper dissection and reconstruction of the paravertebral and deep back muscles are therefore crucial in minimizing the risk of herniation. In this paper, we discuss the mechanisms underlying the development of Grynfeltt–Lesshaft hernia following posterior thoracolumbar stabilization surgery—a procedure that is increasingly performed in neurosurgical practice. We also address the predisposing factors and emphasize the importance of meticulous reconstruction of the musculofascial structures within the superior lumbar triangle to prevent this rare complication.