The main aim of this study was to analyze the effects of availability of key information and intergenerational leadership on burnout divided into physical symptoms of burnout and emotional symptoms of burnout and work engagement regarding the firm size during the coronavirus disease 2019. The empirical study included 583 older employees in Slovenia who participated in the survey during the COVID-19 pandemic. Structural equation modeling was used to explore the effects between constructs. We analyzed structural paths for the entire sample (...) and for the two groups. According to the results concerning both groups, the impact of the availability of key information on emotional burnout is negative only for small companies. Contrary to that the negative impact of intergenerational leadership on emotional burnout is much stronger in large companies. Concerning the impact of physical burnout on emotional burnout, the positive impact of physical burnout exists in both types of companies but is stronger in small companies. The findings will contribute to a clearer picture and the adoption of further measures to prevent burnout in the workplace and increase work engagement concerning the firm size, especially during the COVID-19 pandemic. (shrink)