Point-of-care ultrasound (POCUS) in the diagnoses of postoperative complications is discussed. POCUS is useful in many situations such as abdominal distension, elevated liver enzymes, abdominal pain, and fever, which are the common complications encountered after surgical operations. In the patients with abdominal distention, bowel distention or ascites can be easily detected by POCUS. Occasionally, congestive liver and milk of calcium bile caused by the administration of antibiotics cause elevated liver enzymes, and both of these can also be detected by POCUS. Although there are many complications which cause abdominal pain, POCUS is useful not only for the diagnosis of intraabdominal disorders but also the .diseases of other organs including the bone and muscle. Even the presence of NOMI (non-occlusive mesenteric ischemia) can be diagnosed by contrast ultrasound using Sonazoid®. In patients with fever, US is useful not only for the diagnosis of abdominal abscess but also for the drainage. By evaluating the colon with POCUS, we can detect the pseudomembranous colitis which often is overlooked. In conclusion, POCUS is an essential tool for the proper management of postoperative patients.