Calreticulin (CALR) is a calcium-binding protein chaperone that may be found throughout the extracellular matrix and membranes of cells. It regulates calcium homeostasis and ensures the appropriate folding of newly generated glycoproteins within the endoplasmic reticulum. A somatic mutation in JAK2, CALR, or MPL is responsible for the great majority of essential thrombocythemia (ET) cases. ET has a diagnostic and prognostic value because of the sort of mutation that causes it. ET patients with the JAK2 V617F mutation had more noticeable leukocytosis, higher hemoglobin levels, and lower platelet levels, but also more thrombotic problems and a higher risk of PV transition. CALR mutations, on the other hand, are linked to a younger age group, males, with lower hemoglobin and leukocyte counts, but higher platelet counts, and a higher risk of myelofibrosis transformation. There are two predominant types of CALR mutations in ET patients. Different CALR point mutations have been identified in recent years, but their involvement in the molecular pathogenesis of MPN, including ET, is still unknown. In this case report, we presented a rare CALR mutation in a patient who was diagnosed with ET and followed up.