Abstract Background: Iron-chelating therapy causes improvement in the life expectancy of thalassemic patients. Deferasirox (DFX) is an oral iron chelator with an established dose-dependent efficacy, though alteration of renal function has been observed in many studies. In the present study, we evaluated the effect of treatment with DFX on renal function. Materials and Methods: This quasi-experimental study was done in the Thalassemia Center of Bangladesh Shishu Hospital and Institute from June 2019 to July 2021, where 50 thalassemia major and E-β thalassemia children aged 2–18 years old were included. Blood urea nitrogen (BUN), serum creatinine, spot urinary protein creatinine ratio, spot urinary calcium creatinine ratio, and estimated glomerular filtration rate (eGFR) were measured. If renal functions were normal, DFX was started at a dose of 25 mg/kg/day. After 6 months of DFX treatment, the abovementioned investigations were repeated and analysis was done. The study variables were analyzed by paired t-test. P value <0.05 was considered significant. Results: The mean age of the thalassemic children was 5.21 ± 1.72 years. Before treatment, mean serum creatinine was 39.78 ± 3.12 μmol/L, and after 6 months, serum creatinine was increased but not statistically significant. The mean value was 40.50 ± 3.39 μmol/L after 6 months (P value 0.071). There was no significant change of BUN. Initially, the mean BUN was 3.39 ± 0.76 mmol/L, and 6 months after treatment, it was 3.45 ± 0.70 mmol/L. Initially, the spot urinary protein creatinine ratio was 0.12 ± 0.04, and after 6 months, the mean value was 0.43 ± 0.24. it was significantly increased (P value <0.001). Initially, the spot urinary calcium creatinine ratio was 0.068 ± 0.043, and after treatment, it was significantly raised. The mean value was 0.191 ± 0.168 (P value <0.001). After 6 months of treatment with DFX, 35 patients developed mild proteinuria, and eight patients developed hypercalciuria. There was no significant change of eGFR before and after treatment. Conclusions: In this study, we got significant proteinuria and hypercalciuria but nonsignificant changes in serum creatinine, BUN, and eGFR.