Background: Beta thalassemia is a common inherited disease, resulting from one or more of 200 different mutations in the beta-globin gene. Qazvin province has attracted migrations of several different populations due to industrialization during the past five decades. The aim of this study was to define the molecular spectrum of beta-thalassemia mutations in Qazvin province. Methods: Ethylen diamin acetic acid-containing venous blood samples were collected from 100 patients with transfusion-dependent beta-thalassemia from the department of Pediatrics in Qods hospital. Age, sex, history, and consanguinity between the parents were recorded by reviewing the patients’ files. DNA was isolated from leukocytes using the standard procedure. Amplification refractory mutation system (ARMS) technique was used for molecular detection of mutations. Direct sequencing analysis was applied for DNA samples when no mutation was detected with ARMS. Results: Of the 200 chromosomes investigated, 11 types of mutations were identified by ARMS technique while direct sequencing revealed the remaining alleles (9 types of mutations). Total 20 different mutations discovered by this two-step approach. Abundant alleles (IVS II-1, IVS I-10, FSC 8/9) accounted for 59.3% of the mutations. IVS II-1 with a frequency of 31.3 % was the most common while HbS, Cd 74/75 and Cd 15, each with a frequency of 0.55%, had the least frequencies. Conclusion: Beta thalassemia mutations are very heterogeneous in Qazvin province. Extensive ethnic and genetic admixture has resulted in unexpectedly high number of different mutations, most of them similar to that of north and north-western provinces of Iran. Different mutations in this region suggest migration of chromosomes from distant places and genetic admixture.