OBJECTIVE To reveal the existence of alarms in COVID-19 intensive care units, where medical devices with alarm function are frequently used, the effects of alarms on nurses, especially their on-the-job performances and social lives, and their coping methods. This was a mixed design, including descriptive and qualitative research methods with two stages, and was carried out between March and April 2021. The study adhered to the STROBE checklist for cross-sectional studies and the COREQ guidelines for qualitative studies. METHODS Nurses in the COVID-19 intensive care unit of a university hospital constituted the sample. 58 nurses participated in the quantitative data phase, and 18 nurses in the qualitative interviews. RESULTS More than half of the nurses worked in the COVID-19 intensive care unit for more than 5 months and overtime, and 87.9 had day and night shifts. The monthly income level of 65.5% was between the hunger and poverty lines, and 12.1 % received psychiatric support in the last 6 months. A positive and significant relationship was found between the mean score obtained from the alarm fatigue questionnaire and the level of discomfort felt due to the alarms (1-10 points) (p = 0.001). Five themes and thirty sub-themes were emerged in the focus group interviews. CONCLUSIONS The number of alarms of the medical devices in the COVID-19 intensive care units was more than the other intensive care units, resulting in fatigue in nurses. Since alarm fatigue is directly related to patient safety, the effective management of medical device alarms can reduce alarm fatigue and prevent potentially dangerous outcomes. CONCLUSIONS Nurses care for patients with severe clinical conditions in COVID-19 intensive care units. This situation caused them to be exposed to more alarms. Nurses should make efforts to reduce their alarm intensity.