Primary myelofibrosis (PMF) is characterized by bone marrow fibrosis, myeloproliferation, extramedullary hematopoiesis, splenomegaly and leukemic progression. Moreover, the bone marrow and spleen of patients are full of atypical megakaryocytes that are postulated to contribute to fibrosis through the release of cytokines including TGF-β. Although the JAK inhibitor ruxolitinib provides symptomatic relief, it does not reduce the mutant allele burden or significantly reverse fibrosis. Here we show through pharmacologic and genetic studies that, apart from JAK2, Aurora kinase A (AURKA) is a novel therapeutic target in PMF. MLN8237, a selective AURKA inhibitor promoted polyploidization and differentiation of PMF megakaryocytes and displayed potent anti-fibrotic and anti-tumor activity in vivo. We also reveal that loss of one allele of AURKA is sufficient to ameliorate fibrosis and other PMF phenotypes in vivo. Our data suggest that megakaryocytes are drivers of fibrosis and that targeting them with AURKA inhibitors will provide therapeutic benefit in PMF.