OBJECTIVES: To examine the extent of the impact of the COVID-19 pandemic on the mental health and well-being of mental health professionals (MHPs) in the Netherlands and understand their needs during the COVID-19 pandemic. DESIGN AND SETTING: A cross-sectional, mixed-methods study was conducted with MHPs from the Netherlands from June 2020 to October 2020, consisting of an online survey and three online focus group discussions. PARTICIPANTS: Participants were MHPs from various occupational groups (psychologists, social workers, mental health nurses, developmental education workers, etc). PRIMARY AND SECONDARY OUTCOME MEASURES: The online survey included questions about work-related changes due to COVID-19 perceived resilience to stress, changes in lifestyle behaviours and mental health symptoms. The focus group discussions focused mostly on work experiences during the first wave of the COVID-19 pandemic. RESULTS: MHP's reported an increase in experience workload during the pandemic (mean score 8.04 based on a scale of 1-10) compared to before the pandemic (mean score of 7). During the first wave of the pandemic, 50% of respondents reported increased stress, 32% increased sleeping problems and 24% increased mental health problems. Adverse occupational (eg, increased workload OR 1.72, 95% CI 1.28-2.32), psychological (eg, life satisfaction OR 0.63, 95% CI 0.52-0.75), lifestyle (eg, increased sleep problems OR 2.80, 95% CI 2.07-3.80) and physical factors (decline in physical health OR 3.56, 95% CI 2.61-4.85) were associated with a decline in mental health. Participants expressed significant concern in the focus group discussions about the duration of the pandemic, the high workload, less work-life balance and lack of contact with colleagues. Suggestions to improve working conditions included ensuring clear communication about guidelines and facilitating worker contact and support via peer-to-peer coaching where experiences can be shared. CONCLUSIONS: The current study indicates that MHP experienced a decline in ...