Aim: Positive behaviour support (PBS) is a proactive, person-centred, approach for working with behaviours that are challenging to support. The use of PBS in educational and intellectual disability settings is widely recognised. However, surprisingly few papers have explored the use of PBS in inpatient mental health settings, and, even fewer, the perspective of staff members. This service evaluation aimed to explore staff perceptions and experiences of implementing a PBS model within one psychiatric intensive care unit (PICU). Method: Six members of PICU staff participated in qualitative, semi- structured, interviews to explore their experiences of implementing PBS in their clinical practice. All data was analysed using empirical thematic analysis. Results: Four themes were identified: The practice and principles of PBS, Changes for the better, for all, Emotional and practical challenges and Staff wellbeing and confidence. Conclusion: Staff had positive experiences implementing a PBS model in PICU settings, which appears to translate well to inpatient mental health care. Benefits of PBS were perceived in the ward environment, to patient care and in staff communication, confidence and wellbeing. However, these were dependent upon the availability of resources and support. To ensure sustainable success, the implementation of PBS in PICU settings requires ongoing organisational and leadership support to help staff feel able and confident to deliver model driven care.