Background & Aims: Thalassemia major (TM) is one of the most common chronic genetic disorders in today's world. The number of patients with thalassemia in the world is estimated at 240 million and is reported in 60 countries. Iran is located in the thalassemia belt and has about 26,000 patients with thalassemia major. Patients with chronic diseases such as thalassemia have to undergo continuous medical treatment throughout their lives and their survival depends on these treatments. The treatment protocol affects different aspects of these patients' lives and can make them anxious. Therefore, any measures taken to reduce the anxiety of these patients are very important. Educational intervention can be a method for improving the quality of life in patients with chronic diseases. Nowadays, the educational methods that engage learners in their learning process have acquired attention. One of the methods to educate patients is peer education which has been effective in promoting their health status. In this educational approach, patients share their experiences about their common disease. Having worked in the thalassemia ward, the researcher realized the importance of peer education as a scientific and codified method for efficient education of these patients. Moreover, considering the clinical observation of psychological problems in patients with thalassemia major and also the lack of continuous and reliable research in this field, the present study aimed to evaluate the effect of peer education on the anxiety experienced by patients with thalassemia major. Materials & Methods: This one-group, quasi-experimental study was conducted at Imam Khomeini Hospital in Zabol between March and July 2020 on 50 participants, who were selected via continuous sampling from the patients with the thalassemia major based on the inclusion and exclusion criteria of the study. Data were collected using a demographic questionnaire exploring participants' age, sex, residency, occupation, level of education, economic status, parents' familial relationship, the frequency of blood transfusions per month, another family member with the same disease, the type of iron-chelating agent, regular drug consumption, and history of other diseases. In addition, the valid and reliable Beck Anxiety Inventory (BAI) was used to measure anxiety. The study began with the selection of eligible peers educators based on inclusion criteria. Finally, 2 patients with thalassemia major (a man and a woman) who obtained higher scores were selected as peer educators, who were then trained by the researcher in 3 sixty-minute educational sessions within one week. The educational content included explanations about research objectives, the importance and benefits of peer education, educational concepts, communication skills including attention to verbal and non-verbal behaviors, active listening skills, and anxiety control concepts. The educational content was taught through an interactive lecture using audio-visual aids, and question and answer. Based on the training g...