©Copyright 2021 by the University of Health Sciences Turkey, Gülhane Faculty of Medicine / Gülhane Medical Journal published by Galenos Publishing House.Aims: Primary myelofibrosis (PMF) and post-polycythemia vera (PV) or essential thrombocythemia (ET) myelofibrosis (MF) have many common features in terms of clinical course and laboratory findings. However, there are insufficient studies showing the etiological or morphological differences between these patients. The aim of this study was to compare the hemogram parameters, routine biochemical markers, presence of Janus kinase-2 (JAK- 2) V617F gene mutation and allele burden, and spleen sizes and also to analyze the clinical courses of these two patient groups regarding to thromboembolic complications, leukemic transformation, overall survival (OS), and treatment modalities. Methods: This retrospective study included patients who were diagnosed with PMF and post-PV/ET MF in the Diskapi Yildirim Beyazit Training and Research Hospital between 2008 and 2019. PMF and post-PV/ET MF patients were compared in terms of demographic data, laboratory parameters and clinical features. Results: Evaluation was made on a total of 31 patients (16 PMF, 15 post-PV/ET MF). The mean follow-up period was 31.1 months. JAK-2 mutation was detected in 62.5% of PMF patients and in 80% of post-PV/ET MF patients. Thromboembolic complications developed in 12.5% of PMF patients and in 13.3% of post-PV/ET MF patients. The mean OS of patients was 28.7 months in the PMF group and 18.5 months in the post-PV/ET MF group. No significant difference was observed between the two groups in terms of OS. Conclusions: We found that clinical characteristics of PMF and post-PV/ET MF patients such as hemogram and biochemical values, absence of JAK-2 mutation and allele burden, and spleen sizes were similar. We also found that patients showed a similar clinical course in terms of thromboembolic complications, acute leukemia transformation and survival.