Nosocomial sepsis agents with multidrug resistance have led to higher morbidity and mortality in premature infants in the recent years. Acinetobacter baumannii has become a leading cause of nosocomial sepsis in several neonatal intensive care units. In this study, the demographic, clinic, microbiologic characteristics and risk factors of 21 premature infants hospitalized in newborn intensive care unit between January 2010-February 2011 and developed A.baumannii infection, have been evaluated retrospectively. The isolates were identified by conventional methods and antibiotic susceptibility tests were performed by Vitek 2 GN and AST-N090 using Vitek 2 Compact system (BioMerieux, France). A.baumannii was isolated from the blood samples of 10 patients, central venous catheter samples of three patients, CSF samples of two, tracheal aspirate of two and urine sample of one patient. In two patients both blood and central venous catheter samples and in one patient both blood and CSF samples revealed A.baumannii. Gestational age was between 22-30 weeks and birth weight was between 500-1320 grams (17 were < 1000 g) in 19 patients. A.baumannii caused early onset (≤ 3 days) sepsis in four, and late onset (≥ 4 days) sepsis in 17 patients. The main risk factors were detected as mechanical ventilation (n= 20, 95%), prematurity (n= 19, 91%), total parenteral nutrition (n= 17, 81%) and central catheter use (n= 14, 67%). Antibiotics with highest rates of susceptibility were gentamicin (18/21), amikacin (14/21), and colistin (10/21). Twenty (95%) isolates had multiple drug resistance. Amikacin, gentamicin, colistin and imipenem were used for treatment, however 12 infants, 8 of which due to sepsis, died. In conclusion, A.baumannii which is an important nosocomial sepsis agent with multidrug resistance, is increasing in incidence. To control Acinetobacter infections especially in low-birth weight infants, the use of invasive procedures, total parenteral nutrition and broad spectrum antibiotics should be limited and infected patients should be isolated besides establishment of other appropriate infection control measures.