Introduction: The COVID-19 pandemics presents an urgent situation in public health, which has had an impact at all levels of the society, but mostly on the publich health system and the people who work in it. COVID-19 has definitely had an effect on the mental health of healthcare workers and has caused them different emotional difficulties, by bringing about worries, challenges and doubts and putting them in new and unknown situations. Objective: The aim of this research was to see what were challenges, worries and concerns of the healthcare workers who work with COVID-19 patients at the University Hospital for Infectious Diseases "Dr. Fran Mihaljević" and how it all affects their mental health. Methods: A cross-sectional study has been conducted and approved by Ethic Comitte of University Hospital for Infectious Diseases "Dr. Fran Mihaljević" as well as the Ethic Committee of the Catholic University of Croatia. Physicians and nurses from the University Hospital for Infectious Diseases "Dr. Fran Mihaljević“ took part in the study by completing a survey. Data were analysed, frequency tables were made, arithmetic means and standard deviations were calculated to show the average results of the tested constructs. A t-test for independent samples was used to examine differences in levels of worries and concerns, as well as stress and anxiety between participants. Results: A total of 115 participants were included in this research, of whom 90.4% were nurses and 9.6% were physicians. The difference in exposure to worries at work and at home between nurses and physicians was examined, where the results showed that there was no significant difference in the level of worries and concerns related to COVID-19 at work (t = 1.69, df = 113, p> .0.5) nor at home (t = 0.32, df = 113, p> .0.5) between the two groups. Furthermore, the results show that there is no statistically significant difference in the level of stress and anxiety between male and female respondents in the workplace (t = 1.95, df = 113, p> .0.5) or at home (t = 1.46, df = 113, p> .0.5). The results of the research also show that there is no difference in the level of stress and anxiety at work (t = -1.18, df = 113, p> .0.5) and at home (t = -1.93, df = 113, p > .0, 5) between nurses and physicians who have less than five years of experience and those who have more than five years of experience. Almost half of the nurses and physicians stated that their mental health was worse than before the pandemic (48.7%), while their physical health remained almost unchanged (48.7%). Respondents also expressed the high importance of measures to reduce stress and anxiety levels where six of the eight measures were rated as highly important with an average of 4.02 (SD = 0.70). The scale was marked with values from one to five. The most important measure they marked with an average score of 4.57 (SD = 0.76) was the reduction of working hours and and increase in the staff number. Conclusion: The study has shown that the COVID-19 pandemics has had a significant impact on the mental wellbeing of healthcare workers who need to be provided with help while dealing not only with these issues, but also with other difficulties which they encounter on an everyday basis while working with COVID-19 patients. Gettig them propper help would prevent their mental and physical overload, and would make their everyday working conditions much easier.