Thalassemia, the most common genetic disorder worldwide is a genetic disease in globin chain. Complete absence of beta chain is defined as thalassemia major. These patients suffer from severe hemolytic anemia. Iron overload and chronic immune-stimulation by repeated blood transfusions, splenectomy and alteration in immune system posse these patients to increased risk for severe and serious infections. Several component of immune system may affected by this disease. Increase in number and activity of suppressor T cells (CD-8) in addition to decrease in number and proliferative capacity of helper T- Cells (CD-4) leading to decreased CD4/CD8 ratio, as well as defective activity of natural killer (NK) cells. Immunoglobulin levels and count of B- lymphocytes were found to be increased. Neutrophil chemotaxy activity and macrophages phagocytosis capacity has been defective. Suppressed function of complement system both in classic and alternative pathways, with reduced levels of C3 and C4 has also been reported. Results of various researches about immune system in thalasemic patients are not conclusive and in a lot of reports are controversial.