Abstract: Necrotizing enterocolitis (NEC) yet remains a leading cause of morbidity and mortality in premature infants. The developmental deficiency of transforming growth factor-Beta (TGF-β) in the intestine is a risk factor for NEC in premature infants.We aimed to investigate the potential utility of serum TGF-β1 in the early diagnosis and severity assessment of NEC. This prospective case-control study was conducted on 102 VLBW neonates aging less than 32 weeks and weighing less than 1500 gm. They were divided into NEC group of 52 preterm neonates with symptoms and signs of NEC and 50 age and sex-matched neonates without NEC as a control group. All neonates underwent full medical history taking, clinical examination, radiological and laboratory investigations including CBC, CRP, fecal occult blood, and serum TGF-β1. Serum TGF-β1 was tested in NEC patients at the onset of symptoms and signs and 7 days later. Serum TGF-β1 was significantly lower in NEC patients at the onset of symptoms than the control group (P = 0.004) while after 7 days of onset serum TGF-β1 was significantly higher than at the onset of symptoms (P < 0.001). In NEC patients with stage I, TGF-β1 was significantly higher than in NEC patients with stage ≥II (P = 0.027).In conclusion serum TGF-β1 is downregulated in neonatal necrotizing enterocolitis and can be used as a useful biomarker for early diagnosis of NEC and to assess disease severity.