Introduction: Neonatal sepsis is a common life threatening disease. Although advances in neonatal care have improved survival and reduced complications, sepsis still remains one of the leading causes of morbidity and mortality among both term and preterm infants. Klebsiella spp. is one of the most commonly reported causes of neonatal sepsis in several studies from developing countries. Klebsiella pneumoniae is the most medically important species of the group and has been identified as one of the most frequent causes of outbreaks reported in neonatal intensive care units (NICUs). The emergence of resistant strains to commonly used antibiotics is progressively increasing, giving rise to the importance of studying the most commonly isolated pathogens causing nosocomial outbreaks and their methods of prevention and control. Objective: This prospective study aimed to identify phenotypes of different Klebsiella species in neonatal sepsis in the neonatal intensive care unit and to compare risk factors, clinical presentation , antibiotic sensitivity and outcome of Klebsiella species neonatal infection with the other common pathogens in the unit. Patients and methods: The study was carried on forty five newborns with clinically suspected signs of sepsis with blood culture-proven neonatal bacterial infection in the neonatal intensive care units of Cairo University Pediatric Hospital over a period of 6months. History taking, clinical examination and sepsis work up (complete differential count, CRP, blood culture + other cultures) were done routinely on admission and prior to start of empirical antibiotic treatment. Antimicrobial susceptibility testing was performed and antibiotics were changed. Klebsiella species phenotyping was done using Analytic profile index; API E20 kit which is a standardized identification system for Enterbacteriaceae and other non-fastidious, Gram-negative rods which, uses 21 miniaturized biochemical tests and a database. Results: Klebsiella Spp (48.8%) is the most commonly isolated pathogen causing neonatal sepsis in neonatal intensive care unit followed by CoNS (20%), Pseudomonas (8.8%) and Enterobacter (6.6%). Klebsiella pneumoniae (91%) is the commonest species identified phenotypically . Antibiotic sensitivity of Klebsiella showed highest sensitivity to carbapenems (90%), followed by quinolones (63.6%) and aminoglycosides (59%). Also Klebsiella showed sensitivity to sulpha-cotrimoxazole (22.7%) and polymixin (9%). Highest resistance was reported to ampicillins group. Klebsiella was responsible for 69.2% of overall mortality of neonates with culture proven bacterial infection included in the study during this period.