Mental health conditions such as depression are prevalent in working adults, costly to employers, and areas of social and legal liability for employers. Line managers are crucial in implementing organizational responses to employee mental ill-health but their perspectives are largely unrepresented in literature on workplace mental health promotion. This study aimed to explore situations in which line managers became aware of, and responded to, employees' emergent mental ill-health issues in order to guide theory and practice development. Design: Semi-structured interviews were conducted with 24 Australian managers who had supervised an employee with emerging mental health issues relating to depression or burnout. Interview transcripts were content analyzed to explore themes in managers' experiences. Findings: Managing an employee with an emerging mental health issue involves becoming aware of the issue, taking action to understand the situation and develop an action response, implementing the response and managing the ongoing situation. Each of these tasks had a range of positive and negative aspects to them e.g. managing the situation can be experienced as both a source of stress for the manager but also as an opportunity to develop greater management skills. Practical implications: Understanding line managers' experiences is critical to successful implementation of HR policies regarding employee health and wellbeing. HR strategies for dealing with employee mental health issues need to consider implementation support for managers, including promotion of guiding policies, training, emotional support and creating a psychosocial safety climate in their work units or teams.