WHAT IS KNOWN ON THE SUBJECT?: Interaction between staff and patients with a diagnosis of personality disorder in forensic settings is important for quality of care, but research is lacking on what determines this interaction. WHAT THE PAPER ADDS TO EXISTING KNOWLEDGE?: Insight, emotion-focused coping and emotion regulation of staff influence the interaction between staff and these patients. Staff who understand their own thoughts, feelings and behaviour better (more insight) needed less support, encouragement or back-up from their patients. Staff who cope by getting upset, blaming themselves or fantasizing about solutions (emotion-focused coping) on the contrary needed more support from their patients. Emotion regulation had an impact on the relation between coping and hostile staff behaviour. When staff get upset (emotion-focused coping) and try to think differently about the situation (reappraisal), this makes them behave in a more hostile manner towards their patients. When staff suppress their emotions and also distract themselves or engage in social activities (avoidance-focused coping), they behave in a less hostile manner towards their patients. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: In order to provide compassionate care for their patients, staff ought to be trained in self-compassion. This may help them not to get upset, blame themselves or fantasize about solutions and to understand their own thoughts, feelings and behaviour better. As a result, staff may need less support, encouragement or back-up from their patients. Context is important: Staff ought to suppress their emotions when emotions run high, but only when they also care for themselves by distracting themselves or engaging in social activities. Facing and regulating their emotions by changing what they think about the situation (reappraisal) may be more appropriate once emotions have settled down. This may help staff to remain compassionate towards their patients in the long run and avoid burn-out or compassion fatigue due to ignoring their own needs and boundaries. ABSTRACT: Introduction Research is lacking on what determines interaction between staff and patients with a diagnosis of personality disorder in forensic settings. Aim To test whether coping, self-reflection, insight and emotion regulation are related to the behaviour of staff towards these patients, and to test the possible moderating and mediating effect of emotion regulation. Method Using a cross-sectional design, 76 direct care staff of a forensic clinic completed questionnaires on all variables. Relations were tested using simple linear regression, mediation and moderation analyses. Results Insight and emotion-focused coping of staff were related to seeking less and more support from patients, respectively. Emotion regulation by reappraisal combined with emotion-focused coping was associated with more hostile behaviour by staff, and suppression combined with avoidance-focused coping with less hostile behaviour. Conclusion Insight, emotion-focused coping and emotion regulation of staff influence the quality of care of patients with a diagnosis of personality disorder in forensic settings. Future research ought to include contextual factors. Implications for practice Enhancing self-compassion may improve insight and reduce emotion-focused coping. Context is important: Taking the needs of staff into account may involve suppressing emotions combined with avoidance in a highly emotional situation while facing and reappraising the situation when emotions are low.