The administration of fentanyl for sedation of ventilated newborns can induce several side-effects such as hypertension, respiratory muscle rigidity and, as shown in this report, decreased gastrointestinal motility. We report a case of paralytic ileus in a ventilated preterm infant who was given fentanyl in the first 24 hours of life. To our knowledge, the association of paralytic ileus with fentanyl has not been reported previously in full-term or preterm infants. This study indicates that early recognition is required to shorten the delay in diagnosis.