Late-onset Group B streptococcal (GBS) disease is a cause of illness, death and neurological sequelae in infancy. The epidemiology and pathogenesis of late-onset GBS disease is poorly defined. Infected breast-milk has been suggested as a source of postnatal infection and invasive disease. We describe a late-onset GBS disease by infected mother's milk in a term newborn in which the detection of GBS in neonatal bloodstream (confirmed by culture) and in the mother's milk was performed by PCR.