Incidents of aggression and self-harm in forensic mental health inpatient settings present a significant challenge to practitioners in terms of safely managing and reducing the harm they cause. Research has been conducted to explore the possible predictors of these incidents and has identified a range of environmental, situational, and individual risk factors. However, despite the often interpersonal nature of the majority of aggressive incidents, few studies have investigated forensic inpatient interpersonal styles as predictors of aggression and even fewer have explored the potential interpersonal function of self-harming behaviors. The current study investigated the predictive validity of the Chart of Interpersonal Reactions in Closed Living Environments (CIRCLE) for incidents of verbal and physical aggression, and self-harm recorded from 204 high-secure forensic inpatients. Means comparisons, correlations, and receiver operating characteristics (ROC) were conducted on recorded incident data at 12, 24, and 48 months following baseline assessment using the CIRCLE. Dominant and coercive interpersonal styles were significant predictors of aggression, and a coercive interpersonal style was a significant predictor of self-harm, over the recorded time periods. When categorizing the inpatients on the basis of short- and long-term admissions, these findings were only replicated for inpatients with shorter lengths of stay. The findings support previous research which has demonstrated the benefits of assessing interpersonal style for the purposes of risk planning and management of forensic inpatients. The predictive value may be time-limited in terms of stage of admission.