Abstract Background: Thalassemia Patients frequently experience complications like bone affection and damage. Serum fibroblast growth factor (FGF23)/thalassemia bone disease development is influenced by FGF23. Correlation of FGF23 with serum Calcium (Ca), phosphorus (Ph) and Ferritin level in thalassemia patients is an important step to investigate and treat thalassemia bone disease. Aim of Study: To assess the FGF-23 level in the serum of adult b-thalassemia patients and its correlation to ferritin, calcium, and phosphorus levels. Patients and Methods: Fifty-three patients with b-thalassemia; transfusion dependent thalassemia (TDT) and non-transfusion dependent (NTDT) were included. Any patient with chronic inflammation, renal impairment, or failure were excluded. Serum ferritin, phosphorous, calcium, and FGF-23 were checked and analyzed. Results: Mean age of the studied population was 30±7.6 years, 37.3% males and 62.3% females. TDT were 41.5% & NTDT were 58.5%. Patients suffering from Bony pains were 54.7% and cardiac complications were 18.9%. Significant correlations were found between serum FGF-23 and each of Bony pains and Cardiac complications (p-value <0.001). Significantly negative correlations between serum FGF-23 and each of serum Ferritin & Ca (p-value <0.001). Addi-tionally, FGF-23 and serum Ph level have a strong positive correlation (p-value <0.001). Conclusion: FGF-23 was significantly correlated with (Ferritin, Ca, & Ph levels), Suggesting its participation in Ca homeostasis and thalassemia bone disease. Further studies with larger number of patients is required for more under-standing to FGF-23 role in thalassemia and its complications.