Background: Thalassemia is a hereditary hemolytic anemia with a severity ranging from mild, non transfusion-dependent to severe chronic anemia requiring lifelong transfusion. Transfusional iron overload is a major complication in patients with transfusion-dependent thalassemia (TDT). Telomeres are sequences of nucleotides forming the end caps of chromosomes that act as a DNA repair system. Iron overload in thalassemia can cause increased oxidative stress which leads to cellular damage and senescence. This may result in telomere length shortening. The degree of telomere length shortening may reflect the severity of thalassemia. Methods: This research aimed to study the telomere length in patients with TDT in comparison to non-thalassemic individuals and to identify the clinical and laboratory parameters that are associated with telomere length. We conducted a cross-sectional study in patients with TDT aged ³18 years. Telomere length was measured by real-time quantitative PCR. Results: Sixty-five patients with TDT were enrolled onto the study. There were 37 female patients (54.4%). The median age was 27 (18-57) years, and mean pre-transfusion hemoglobin (Hb) was 7.1 (± 1.07) g/dL. The mean telomeric terminal restriction fragment length (TRFL) of patients with TDT and the controls was 6.11 (± 0.61) kb and 6.79 (± 0.84) kb, respectively (p <0.0001). There was a significant correlation between TRFL and age (p =0.0002), and Hb (p=0.044). There was no correlation of telomere length with other factors. Conclusions: Our study showed that TDT patients had shorter telomere length compared with controls. Telomere shortening in TDT was an aging-dependent process and associated with lower hemoglobin level.