A pair of preterm twins developed fatal necrotizing enterocolitis (NEC) in association with Staphylococcus epidermidis septicaemia after receiving contaminated expressed breast milk (EBM). S. epidermidis NEC can be associated with severe bowel inflammation, high morbidity and mortality. Breast milk is the most suitable nutrient for preterm infants but EBM should undergo regular screening for bacterial overgrowth. We urge caution before administering EBM found to be heavily contaminated with S. epidermidis to preterm infants.