Background/aim: The purpose of this study was to evaluate nosocomial infections occurring in our hospital intensive care units (ICUs) and the risk factors for these, and to determine the effect of these infections on mortality and cost. Materials and methods: This retrospective study was performed via infection control committee surveillance data, ICU records, and information processing data between 1 January and 31 December 2013 at the Kanuni Education and Research Hospital. Results: A total of 309 nosocomial infections were observed in 205 out of 566 patients. The density of nosocomial infections was 25.4 in 1000 patient days. Hospitalization was prolonged, and APACHE II and Charlson comorbidity scores were high in patients developing nosocomial infections (P < 0.001). Of the patients diagnosed with a nosocomial infection, 170 died. Infections were determined as the cause of death in 62 (36.5%) of the nonsurviving patients with a nosocomial infection. Acinetobacter baumannii was identified in 46 (74.2%) of the patients that died from nosocomial infections. The mean cost in patients developing a nosocomial infection was 15,229.30 Turkish lira (TL), compared to 9648.00 TL in patients without a nosocomial infection (P = 0.002). Conclusion: Regular infection control education sessions need to be held and the number of nurses needs to be increased in order to be able to reduce this high mortality, morbidity, and cost.