In this article, we review the potential complications of spinal instrumentation discussing various types of postoperative complications. Surgical implants in spinal surgeries are used to stabilize the spine, replace the defective parts and maintain anatomic reduction. Internal spinal instrumentation has undergone considerable advances during the last century. However, the spinal instrumentation is an invasive surgery, and postoperative complications occur frequently after the spinal deformity surgery. Elderly patients, who may have many histories of medical complications and osteoporosis, have a higher complication rate. Pulmonary complications are the most common life-threatening postoperative complications. The acute onset of neurologic symptoms in the immediate postoperative period should arouse clinical suspicion about the possible formation of a hematoma. Such occurrences require urgent surgical decompression. Better recognition of postoperative risk factors and early detection of urgent signs may lead to decrease complication rates and may improve outcomes. Although the latest monitoring system is very useful we should recognize that the observation of the patients by the five senses is the most important way to detect the postoperative medical complications early.