During the coronavirus disease 2019 (COVID-19) pandemic, otolaryngologists should be careful when performing upper airway surgery because of the risk of aerosol generation.This paper describes the case of a 23-year-old male who was diagnosed with COVID-19 four days after undergoing tonsillectomy. COVID-19 was complicated by pulmonary thromboembolism, and anticoagulation was administered, which caused postoperative hemorrhage. The patient had to undergo another surgery for the control of hemorrhage, during the infective period of COVID-19.COVID-19 is sometimes associated with venous embolism, and for postoperative patients, treatment should be carefully considered because of the risk of bleeding. The administration of heparin as an anticoagulant would be preferable because heparin allows for dosage adjustment by measuring activated partial thromboplastin time and also allows the rapid cessation of the anticoagulant effect when the administration is discontinued together with antagonization by protamine administration, even if bleeding occurs. When performing surgery for patients with COVID-19, special care is necessary in order not to spread the infection. Even if the preoperative polymerase chain reaction (PCR) test is negative, the patient may be in the incubation period of COVID-19; therefore, caution should be exercised when performing upper respiratory tract surgery such as tonsillectomy.