Background: Better survival of thalassemia patients allowed previously unrecognized renal complications to emerge. Objectives: Assess prevalence and early predictors of renal dysfunction in young β-thalassemia major (β-TM) and intermedia (β-TI) patients. Subjects: 66 β-TM (group I), 26 β-TI (group II) Egyptian patients and 40 healthy controls. Methods: History, examination and investigations that included kidney function tests, serum ferritin, serum bicarbonate, plasma osmolality and urinary total proteins, microalbuminuria (MAU), N-acetyl-β-D-glucosaminidase (NAG), retinol binding protein (RBP), α-1 microglobulin, bicarbonate, osmolality, Creatinine clearance (CrCl), % fractional excretion of bicarbonate (% FE-HCO3). Results: The most common renal abnormality was proteinuria (71%), followed by increased urinary level of RBP (69.4%), NAG (58.1%), α-1 microglobulin (54.8%) and microalbumin (29%) and also decreased urinary osmolality (58.1%). Although serum creatinine and BUN were not statistically different between thalassemia patients and control, CrCl were significantly lowered in thalassemia patients. Total serum protein and albumin was significant lower in splenectomized β-TM, whereas urinary total protein and MAU were significantly increased in all thalassemia patients. NAG, RBP and α-1 microglobulin were negatively correlated with CrCl and positively correlated with serum ferritin and urinary total protein. Z-score analysis for discrimination of patients with renal dysfunction proved superiority of urine total protein and RBP. Comparative statistics of different frequencies revealed significant difference between the urinary total protein and both MAU and % FE-HCO3. Conclusion: Asymptomatic renal dysfunctions are prevalent in young β-TM and β-TI patients that necessitate regular screening and urinary total protein and RBP may be cost-effective for early detection.