Objectives: The aim of this study was to research the prevalence of superinfections in mechanically ventilated COVID-19 patients and to examine the difference in age, sex and comorbidities between patients without superinfection and with superinfection. The aim was to examine the length of ICU stay and outcomes among the two groups of COVID-19 patients. Study Design: Cross-sectional study Participants and Methods: The study included 315 SARS-CoV-2 positive patients hospitalized at Intensive care unit of the Clinical Hospital Centre Osijek during 2020. The patients were divided into group of patients without or with superinfection depending on the result of positive microbiology specimen or PCT levels of > 1,00 μg/L. The data were obtained from the disease history analysis and therapeutic lists and the differences between two groups were analysed. Statistical analysis was performed using Chi-square test, Mann Whitney U test and Wilcoxon test. Results: The median age of patients was 69 years and hypertension was the most frequent comorbidity (80,3 %). Overall, 70,2 % (221) of patients developed superinfection, 37,1 % blood-stream infection, 35,6 % respiratory infection and 8,3 % urinary infection. Patients with secondary infections had increased length of ICU stay, increased mortality rate (87,3 %) and 95,2 % of them were intubated and required prolonged invasive mechanical ventilation. Acinetobacter baumanii was the most commonly isolated pathogen and was isolated in 51,2 % (124) of patients. Patients who developed superinfection had significantly higher levels of leukocytes, CRP and PCT at ICU admission. Conclusion: COVID-19 patients who have developed superinfection had significantly higher mortality rates, were more frequently intubated, required prolonged invasive mechanical ventilation and longer ICU stay.