Objectives: To illustrate the clinical course and difficulties in early diagnosis of coronavirus disease 2019 (COVID-19) in patients after thoracic surgery. Methods: We retrospectively analyzed the clinical course of the first 11 patients diagnosed with COVID-19 after thoracic surgery in early January 2020. Postoperative clinical, laboratory, and radiologic records and the time line of clinical course were summarized. Potential prognostic factors were evaluated. Results: In the 11 confirmed cases (3 female, 8 male), median days from symptom onset to case detection was 8. Insidious symptom onset and misinterpreted postoperative changes on chest computed tomography (CT) resulted in delay in diagnosis. There were 3 fatalities due to respiratory failure, whereas 4 severe and 4 mild cases recovered and were discharged. All patients had once experienced leukocytosis and eosinopenia. Remittent fever and resected lung segments ≥5 were associated with fatality. Conclusions: The case fatality rate of postsurgical patients subsequently diagnosed with COVID-19 was 27.3%. Insidious symptom onset, postoperative leukocytosis with lymphopenia, and postsurgical CT changes overshadowed the early signs of viral pneumonia. Dynamic symptom monitoring, serial chest CTs, and tests for viral RNA and serum antibody improve the chance for prompt detection of COVID-19. Consideration should be given to preadmission and preoperative screening and strict contact isolation during the postoperative period. © 2020 The American Association for Thoracic Surgery