To investigate whether laboratory markers obtained at the onset of necrotising enterocolitis (NEC) predict the severity of the disease in preterm infants. Prospective cohort study conducted in a tertiary referance hospital. A total of 88 preterm infants were included in the study. Of those, 60 infants had the diagnosis of severe NEC, while the remaining 28 infants constituted the non-severe NEC group. Severe NEC was defined as surgical NEC or NEC-related mortality. Infants with and without severe NEC were compared in terms of demographic, clinical and laboratory characteristics. At the onset of disease, infants with severe NEC noted to have lower platelet count and serum ALB levels (p = 0.011, p = 0.004; respectively), whereas higher CRP, and serum lactate levels (p = 0.009, p = 0.008; respectively). Multiple binary logistic regression analyses showed that CRP (1.03(1.01-1.05), p = 0.024) and serum albumin level (0.16(0.04-0.64), p = 0.010) were statistically significant independent risk factors for severe NEC. The optimal cut-off value for the serum ALB level was found to be 23g/L with 52% sensitivity (95%CI: 37-68%) and 84% specificity (95%CI: 60-97%) (AUC 0.727; p = 0.002). Serum ALB level at NEC onset might be a reliable biomarker for severe disease in preterm infants.