Background: The application of Positive Behavioural Support (PBS) has been widespread across educational and learning disability settings, typically in supporting individuals who exhibit challenging behaviour. Following espousal in various national policy and guidance, PBS is now being applied in the area of secure forensic adult mental health. To date, very little is known about the application of PBS in this area. This study aims to understand how staff within a secure forensic adult mental health setting perceive the application of PBS. Method: Using semi-structured interviews, 11 multi-disciplinary staff members were interviewed regarding their perceptions of PBS. The data was collected and subject to a qualitative thematic analysis. Results: Five themes were identified from the data relating to staff perceptions of PBS, these were: 'The functions', 'Appraising a new approach', 'Collaborative challenges', 'Staff variables' and 'Organisational issues'. Conclusion: PBS translates to a forensic mental health setting and is generally appraised positively by staff. There are however a number of issues that are perceived to impact the delivery of PBS, many of these are consistent with existing PBS literature, however a number arise from the unique nature of providing an approach underpinned by social role valorisation in a context of containment and disempowerment.