In this study, we aimed to determine the epidemiological characteristics of infections detected in a tertiary ICU of our hospital and to evaluate the transmission routes. Material and Method: A total of 1278 patients who were followed up in the ICU for two years were analyzed retrospectively. Health-care associated infection (HAI) diagnoses were evaluated according to the "Centers for Disease Control and Prevention (CDC)" criteria. Results: Fifty-seven of the patients who were followed up were diagnosed with HAI, and 54 pathogens were detected. The rate of HAI development among patients hospitalized in the ICU was 5.24%. In this unit; mechanical ventilator day was 3483, rate of ventilator utilization was 51%, speed of VAP was 0.86, UC day was 6734, rate of UC utilization was 100%, speed of CR-UTI was 0.89, CVC day was 4327, rate of CVC utilization was 63%, speed of CVCR-BSI was determined as 3.93. Pneumonia with specific laboratory findings was the most common infection in patients with HAI (33.4%). Other infections of the lower respiratory tract (31.6%), CVCR-BSI (14%), CR-UTI (7%), VAP (5.2%), clinically defined pneumonia (5.2%),soft tissue infection (1.8%) and laboratory-proven BSI (1.8%) respectively, were followed. Eleven different microorganisms were determined as the pathogens of HAI. The bacteriological profile causing HAI in the study, Gram-negative and Grampositive pathogens were 87,1% and 12.9%, respectively. Acinetobacter baumanni was the most common pathogen (51.9%). Other pathogens were Pseudomonas aeruginosa (11.1%), Klebsiella pneumoniae (9.3%), Staphylococcus aureus (5.6%), Escherichia coli (5.6%), Stenotrophomonas maltophila (5.6%), Enterococcus faecium (3.7%), Acinetobacter lwoffi (1.9%), Enterococcus faecalis (1,9%), Coagulase-negative staphylococcus (1.9%) and Enterobacter cloacae (1.9%). Conclusion: Each unit should determine its patient profile, flora and resistance patterns by conducting surveillance studies and plan treatment strategies accordingly.