Objective: To describe an outbreak of Serratia Marcescens infection in the neonatal intensive care unit at King Hussein Medical Center. Methods: This retrospective review was conducted in the neonatal intensive care unit at King Hussein Medical Center during the period between March 1 and May 30, 2007. The medical and laboratory records of 145 neonates who were admitted to the neonatal intensive care unit during the study period of the outbreak were reviewed. Blood culture, urine culture, swab cultures from the throat, ears, eyes, rectum and umbilicus were performed for the entire study group. Simple descriptive statistical methods (frequency, mean and percentage) were used to describe the study variables. Environmental cultures were taken from potential environmental sources in neonatal intensive care unit and delivery rooms. Results: Thirty-one cases of Serratia Marcescens sepsis were identified, 19(61%) neonates were males and 12(39%) were females. the median age at presentation was six days. Neonates with Serratia Marcescens sepsis were found to have low birth weight, low gestational age, and high rate of mechanical ventilation and central venous catheterization with high overall mortality rate. Conclusion: Although the frequency of Serratia Marcescens in neonatal intensive care units is uncommon, it can cause rapidly spreading outbreaks associated with fatal outcomes.