ABSTRACT Background: Beta Thalassemia is a genetic disorder inherited by autosomal recessive and occurs throughout the world, including Iraq. Patients with beta-thalassemia require blood transfusions for life, and this can lead to the accumulation of iron in the skin, kidneys, and liver, resulting in a decrease in vitamin D synthesis. Methodology: This cross-sectional study was conducted at the Hereditary Blood Disorder Center in Ibn Al balady Hospital in Al Rusafa side in Baghdad from May to August 2023. The population of this study was children and adolescents diagnosed with beta-thalassemia major and on regular blood transfusions. Serum 25-OH-vitamin D, Serum calcium, and Serum ferritin were assessed in those patients. Result: Out of 100 patients involved in this study, (38%) were children and (62%) were adolescents, the male-to-female ratio was 0.52. The mean age of the studied sample was 11.52±4.094 years. The mean 25-OH Vit D level was 24.94±14.66 ng/ml, only 23% of the patients had normal levels of serum vitamin D concentration, 56% had deficient levels and 21% had insufficient levels. The mean serum Ca level was 2.28±0.18 mmol/l, only 19% had low total serum calcium levels, 2% had high levels, and 79% had normal serum calcium levels. The mean serum ferritin level was 3940.48 ± 2287.76 ng/ml, no one had a normal serum ferritin level. Conclusion: A high prevalence of 25 hydroxy vitamin D deficiency and insufficiency levels among thalassemia patients is found, so frequent monitoring and appropriate therapeutic interventions to maintain normal levels of serum vitamin D are indicated to improve bone health and quality of life of those patients. Also, high levels of serum ferritin were noted among those patients who need frequent follow-up and proper chelation therapy.