Background: Trials of complex interventions should be preceded by in-depth piloting of the treatment in order to ensure clear definition of critical components and establish feasibility and acceptability. Objectives: This study aimed to elicit views of extending behavioural activation, an evidence-based treatment for depression, to the negative symptoms observed in psychosis from the perspectives of carers of people with mental health problems and mental health professionals. Design: Qualitative study. Setting: School of Nursing, Midwifery and Social Work and carer support organisation, North West of England, United Kingdom. Participants: Fifteen participants were recruited from a local carer support group. Nineteen mental health professionals were recruited from post-registration university based programmes. Methods: We used focus groups and semi-structured interviews. Thematic analysis using a constant comparative approach was employed to capture key concepts and themes. Results: There was support for behavioural activation for negative symptoms in psychosis from some mental health workers and many of the carers; however both groups identified barriers to its implementation. Professionals highlighted internal factors, the difficulty in engaging people with negative symptoms in psychosocial treatments and services more broadly while carers identified a number of external, practical barriers. For those who saw some utility in the treatment approach, the benefit of expanding the treatment to include community based sessions as well as formal behavioural activation meetings were recognised. However, a number of mental health professionals remained sceptical as to its potential to reduce negative symptoms. Professional and carer views generally concurred in relation to family involvement, indicating that restricted engagement could be helpful, but that further participation might actually be counterproductive. Conclusions: Acceptability for many carers and some professionals was evident and support further evaluation of behavioural activation for negative symptoms. Significant issues to be addressed include the balance of formal talking based sessions and community based sessions to support activation for people with negative symptoms and mental health professional pessimism in relation to this symptom cluster. The current study supports the phased development and careful piloting of complex healthcare interventions before progression to large scale evaluation.