BACKGROUND/AIM: Hyperparathyroidism is an endocrine disorder characterized by hypercalcemia. Because of calcium’s effects on parathyroid glands, bone, intestines, and kidneys, it has an important place in homeostasis. The results of studies regarding hyperparathyroidism hemostasis are conflicting. Thromboelastography helps to evaluate all steps of hemostatic system. Our aim in this study was to investigate the possible role of hemostatic mechanisms in the development of thrombosis in hyperparathyroid patients with the modified rotation thromboelastogram (ROTEM). MATERIALS AND METHODS: Twenty-two patients with primary hyperparathyroidism (PHPT) and 20 healthy controls were involved. This study was conducted in Eskisehir Osmangazi University Faculty of Medicine, Endocrinology and Hematology clinics for 2 years. The complete blood count, fibrinogen, D-dimer levels, prothrombin time, activated prothrombin time, and ROTEM parameters [clot formation time (CFT), clotting time (CT), and maximum clot formation (MCF)] were determined by two activated tests, INTEM and EXTEM analyses. A thromboelastographic evaluation was performed in the preoperative and postoperative (3 months after surgery) periods. RESULTS: In INTEM assay, the CT (p = 0.012) and CFT (p = 0.07) values were increased in preoperative PHPT patients compared with the control group. Although there was a decrease in the postoperative CT and CFT values, no statistical difference was found. CONCLUSION: The prolongation of the CT and CFT values were consistent with a hypocoagulable state in patients with PHPT. Hyperparathyroidism causes a hypocoagulable state that can be successfully assessed by ROTEM. Hemostatic changes, do not seem to have an effect on increased cardiovascular mortality.