Introduction: Calreticulin (CALR) mutations are one of the molecular markers that has been incorporated for the diagnosis of myeloproliferative neoplasms (MPN) in the revised 2017 WHO Classification of Haematopoietic and Lymphoid Tumors. This study was performed to determine the prevalence of CALR mutations in patients with MPN diagnosed in UKMMC and to compare their demographics plus laboratory features with other MPN patients. Methods: A total of 59 MPN patients who tested negative for JAK2V617Fmutation were selected and 21 MPN patients positive for JAK2V617F were included as controls. Screening for CALR exon 9 was done by multiplex polymerase chain reaction (PCR) followed by Sanger sequencing. Results: A total of six JAK2 V617F negative MPN samples were found to be positive for CALR mutations. Out of these six, three patients with CALR mutations were of type I mutation, two were type II while one was a mutation in the stretch III region. None of the twenty one JAK2 V617F positive MPN samples were positive for CALR mutation. Clinical phenotypes for those positive for CALR were restricted to Essential Thrombocythemia (ET), Primary Myelofibrosis (PMF) and one case of atypical Chronic Myeloid Leukaemia (CML). Conclusion: CALR mutations constituted 10.16% from the MPN patients who were negative for JAK2V617F mutation with no significant differences in platelet counts, hemoglobin (Hb), hematocrit and white cell counts as compared to MPN patients with JAK2 V617F mutations. Testing for CALR mutations among those who are negative for JAK2V617F within Malaysian population maybe worthwhile and require larger scale studies.