Activation of the canonical wingless-related integration site (Wnt)/beta-catenin signaling pathway is associated with malignant transformation, development of fibrosis, and angiogenesis. We analyzed beta-catenin mRNA expression in bone marrow of 29 patients with primary (PMF), 4 with secondary (SMF) myelofibrosis, and 16 control participants using quantitative real-time polymerase chain reaction (qRT PCR). beta-Catenin expression is increased in PMF and SMF and might potentiate anemia. Introduction: beta-Catenin is a central effector molecule of the canonical wingless-related integration site (Wnt) signaling pathway. It is important for maintenance of stem cell homeostasis and its aberrant activation has been implicated in a wide array of malignant hematological disorders. There are few reports suggesting its dysregulation in Philadelphia chromosome-negative (Ph-) myeloproliferative neoplasms (MPNs). Patients and Methods: We analyzed beta-catenin mRNA expression in bone marrow (BM) aspirates of 29 patients with primary (PMF) and 4 patients with secondary, post Ph- MPN, myelofibrosis (SMF) using quantitative real-time polymerase chain reaction (qRT PCR). The control group consisted of 16 BM aspirates from patients with limited-stage aggressive non-Hodgkin lymphoma without BM involvement. We compared relative gene expression with clinical and hematological parameters. Results: Relative expression of A-catenin differed significantly among groups (P = .0002), it was significantly higher in patients with PMF and SMF than in the control group, but did not differ between patients with PMF and SMF. A negative correlation was found regarding hemoglobin level in PMF (P = .017). No association according to Janus kinase 2 (JAK2) V617F mutational status or JAK2 V617F allele burden was detected. Conclusion: Our results show for the first time that beta-catenin mRNA expression is increased in patients with PMF and SMF and its upregulation might potentiate anemia. A number of inflammatory cytokines associated with PMF are capable of mediating their effects through increased beta-catenin expression. Accordingly, beta-catenin can induce expression of a number of genes implicated in processes of cell cycle control, fibrosis, and angiogenesis, which are central to the PMF pathogenesis. Therefore, beta-catenin might represent an interesting new therapeutic target in these diseases.