Differentiation syndrome (DS) is a relatively common and severe complication in acute promyelocytic leukemia (APL) patients undergoing induction therapy with all-trans retinoic acid (ATRA) and/or arsenic trioxide (ATO). DS is a multisystem disorder with pulmonary involvement. The coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is also a systemic disorder with similar pulmonary and other clinical manifestations as DS. Here, we report an APL case with overlapping between DS and COVID-19. After admission to the hospital, the patient was diagnosed with APL and underwent differentiation therapy with ATRA/ATO. In the meantime, COVID-19 was diagnosed with a positive polymerase chain reaction test of SARS-CoV-2 from an oropharyngeal swab. The patient developed acute respiratory distress syndrome, coagulopathy, and acute kidney injury, which fit the clinical pictures of both DS and COVID-19. The patient died at last and this complicate case imposed big challenges for clinicians due to the laboratory and imaging findings of DS disguised in the context of COVID-19. Therefore, comprehensive treatment strategy should be considered to balance the risk and benefit of differentiation therapy in the context of COVID-19.