We report a case of clinically diagnosed secondary organizing pneumonia (SOP) associated with coronavirus disease 2019 (COVID-19). A 70-year-old woman who had been diagnosed with COVID-19 was admitted to Hokkaido University Hospital. Although her fever, cough, dyspnea, and serum C-reactive protein levels improved, she developed rapidly progressive respiratory failure and computed tomography revealed the development of bilateral lung consolidation. Her dyspnea was relieved, and her oxygenation levels and radiological findings improved after commencing corticosteroid treatment. Blood biomarkers for interstitial lung disease, Krebs von den Lungen-6 (KL-6) and surfactant protein D (SP-D), showed different responses during the clinical course of her disease. Evaluation of serial changes in levels of KL-6 and SP-D may help diagnose and monitor COVID-19-associated organizing pneumonia (OP). Clinicians should be aware that SOP can develop in response to COVID-19 and that these patients may benefit from the use of steroids.