Myelofibrosis (MF) is a clonal stem cell disorder characterized by ineffective erythropoiesis and extramedullary hematopoiesis leading to progressive bone marrow failure, severe anemia, constitutionalsymptoms, hepatosplenomegaly, and thrombosis.MF can arise following a history of polycythemia vera (PV) or essential thrombocythemia (ET), or canpresent de novo as primarymyelofibrosis(PMF). The disease course is variable with median survival ranging from months to years. Clinical and biological features such as advanced age, leukocytosis, anemia, transfusion dependence, and elevated inflammatory markers can impact prognosis in patients with PMF. Cytogenetic abnormalities and molecular markers such as JAK2 V617F, ASXL1, and CALR mutations have also been identified as prognostic variables. Several different scoring systems have been developed based on these prognostic factors. In this review, we will discuss the clinical, biological, molecular, and cytogenetic prognostic factors that have been identified in PMF, and the current prognostic models that have been developed to guide treatment decisions.