Reactive myelofibrosis (MF) may be associated with infectious, inflammatory, or neoplastic conditions. Extensive myelofibrosis and indolent course are frequent in acute megakaryoblastic leukemia, but these findings are rarely reported in acute promyelocytic leukemia (APL). Patients with neoplastic disorders associated with MF are reported to have an inferior outcome. However, the effect of this association is not apparent in APL patients. This report presents a case of APL in a pediatric patient in association with significant reticulin fibrosis and osteosclerosis. The case highlights that fibrosis in the marrow can make it more challenging to diagnose acute leukemia. ThePML-RARAtranscripts can be present with subtle clinical or hematological findings, emphasizing the importance of molecular studies in unexplained cytopenias. Furthermore, in the case of APL, as opposed to other myeloid neoplasms, fibrosis does not appear to be associated with a worse prognosis and can resolve after treatment.