The 2022 WHO revision and the ICC classification have recently modified the diagnostic criteria for chronic myelomonocytic leukemia (CMML) and acute myeloid leukemia. However, there is no consensus on whether CMML with NPM1 mutation (NPM1mut) should be diagnosed as AML. Nowadays, it is a subject of discussion because of its diagnostic and therapeutic implications. Therefore, we describe a case of a patient diagnosed with CMML NPM1mut and briefly review the literature to highlight the uncertainty about how to classify a CMML with NPM1 mutation. We emphasize the importance of a comprehensive molecular study, which is crucial to optimize the individualized treatment of patients, enabling them to access targeted therapies.