BACKGROUND: There is a growing interest in managers’ wellbeing due to the observed associations between their wellbeing and leadership behaviours, and between leadership behaviours and employees’ wellbeing. However, it is still unclear how managers’ wellbeing influences their practiced leadership across different workplace contexts, which specific behaviours are affected, and how this varies across time. OBJECTIVE: The purpose of this study was therefore to explore managers’ and employees’ experiences and perceptions regarding the consequences of managers’ wellbeing for their leadership behaviours in small businesses. METHODS: Semi-structured interviews were conducted with 37 participants (19 managers and 18 employees) working at 12 Swedish small firms, and analysed using content analysis. RESULTS: The findings show that managers were more constructive when they felt well, and more passively destructive when unwell. Variations in managers’ wellbeing influenced their mood, energy level, and performance, as well as the company’s working climate. However, these destructive leadership variations did not have a substantial impact, because several protective factors were present. CONCLUSION: This study shows that the wellbeing of managers in small businesses has perceptible consequences for their leadership behaviours. The study also shows that sustained leadership behaviours may coexist with temporary variations of these behaviours on a constructive-destructive continuum depending on the leader’s wellbeing. Overall, the findings contribute to a more nuanced and dynamic understanding of how the interaction between managers’ wellbeing and their behaviours unfolds in the particular context of small companies.