Background: There is evidence to suggest a relationship between the way in which staff perceive challenging behaviour and burnout in staff working with people with intellectual disabilities (ID) and challenging behaviour. However, the evidence of a direct link is equivocal and it is possible that a number of different variables mediate this relationship. The aim of the study is to confirm whether there is a relationship between challenging behaviour and staff burnout, and in addition, to test whether staff perceptions about challenging behaviour mediate this relationship. Method: Seventy-eight staff completed measures of burnout, challenging behaviour and perceptions about challenging behaviour. The perceptions explored included beliefs about the timeline of behaviour, staff's perception of whether they themselves have control over the behaviour, beliefs about clients' ability to control the behaviour and staff's negative emotional responses. Results: Significant positive correlations were found between challenging behaviour and burnout, challenging behaviour and cognitive variables, and cognitive variables and burnout. Regression analyses demonstrated that negative emotions mediate the relationship between challenging behaviour and burnout. Conclusions: The results show evidence that there is a relationship between challenging behaviour and burnout that is mediated by negative emotion, namely the fear of potential assault.