Acinetobacter plays an important role in the infection of patients admitted to hospitals. Acinetobacter are free living gram-negative coccobacilli that emerge as significant nosocomial pathogens in the hospital setting and are responsible for intermittent outbreaks. The aim of this study was to determine the prevalence of Acinetobacter in patients admitted into the Intensive Care Unit, identify risk factors associated with infection, the antibiotic susceptibility profile of the isolates and determine the relatedness of the Acinetobacter isolates. A cross sectional study was carried out in the Intensive Care Unit of the University College Hospital Ibadan. Samples collected were tracheal aspirate, catheter specimen of urine, wound biopsy, and blood all for microscopy, culture and sensitivity. The isolates were tested against various antibiotics and the plasmid profile done to determine their relatedness. All data were analyzed using the statistical package for Social Sciences version 15.0 program. Fourteen (14%) of the 100 patients recruited into the study, developed Acinetobacter infection, it consisted of 9% of the total number of isolates isolated. Twelve (86%) of the isolates were recovered from tracheal aspirate, 1(7%) from urine and 1(7%) from blood. Only duration of endotracheal intubation specifically an 8-14day period was an independent risk factor for Acinetobacter. All the isolates were resistant to Ceftriaxone, Ciprofloxacin, Ofloxacin, and gentamicin. Nine (64.3%) of the isolates were susceptible to Meropenem, seven (50%) were susceptible to amikacin and five (35.7%) susceptible to levofloxacin. All of the isolates harbor plasmids of varying molecular sizes. Ten of the fourteen Acinetobacter were isolated at about the same period of time in the ICU with 6(42.7%) having plasmid size in the 23.1kb band and show similar pattern revealing that the isolates exhibit some relatedness. The clonal nature of the isolates suggest that strict infection control practices must be adopted in ICU, also an antibiotic policy must be developed for the ICU to prevent abuse of antibiotics that may lead to selection of resistant bacteria.