Neonatal infective endocarditis is a rare condition and usually pertains to a specific class of immunologically depressed preterm infants, with a long history of invasive procedures in the Neonatal Intensive Care Unit. We report the case of an aggressive and fatal neonatal infective endocarditis in a full-term infant, who developed massive endocardial vegetations on the tricuspid valve, leading to persistent pulmonary hypertension of the newborn, unresponsive to nitric oxide ventilation. Post-mortem cardiac cultures were positive with Serratia marcescens, an unusual germ for an early-onset infection, which was absent in blood cultures.