Transformation from chronic myeloproliferative neoplasm to acute leukemia is a feature of myeloproliferative neoplasm; however, the rate is not high. Transformation to acute promyelocytic leukemia is rare. Here, we report a case of transformation of polycythemia vera to acute promyelocytic leukemia and describe a process of clonal evolution that has not yet been reported. In this case, a 51-year-old woman was diagnosed with polycythemia vera and concomitant JAK2/V617F mutations in July 2019. She underwent intermittent phlebotomy and oral hydroxyurea irregularly. After 2 years, the patient complained of fatigue and poor sleep quality for 2 months. Further examination revealed marked hypercellularity and grade 1 bone marrow fibrosis with the PML/RARαV variant (23.85% mutation load), WT1-Exon1 (37.8%), WT1-Exon9 (4.1%), JAK3-Exon7 (49.3%), and RELN-Exon55 (45.8%). According to the World Health Organization classification of tumors of hematopoietic and lymphoid tissues, the patient was ultimately diagnosed with a rare transformation of polycythemia vera to acute promyelocytic leukemia. The patient underwent dual induction therapy with all-trans-retinoic acid and arsenic trioxide. After 28 days of induction therapy, the patient achieved complete remission, was compliant and the treatment was well tolerated. Polycythemia vera can transform into acute promyelocytic leukemia; therefore, it is important to review bone aspiration and other tests to perform a comprehensive assessment and monitor the disease status, to detect disease progression and intervene early when it transforms into acute promyelocytic leukemia.