Background: This study examines associations between group climate, aggressive incidents and coercive measures in adults with mild intellectual disability or borderline intellectual functioning (MID-BIF) of a secure forensic setting. Method: Participants (N = 248) were interviewed about their perception of group climate utilizing the Group Climate Instrument. Data on aggressive incidents and coercive measures were retrieved from the facilities' electronic database. A multilevel structural equation model was fitted in which variability in perception of group climate within and between living groups was examined. Results: An open and therapeutic group climate was associated with lower levels of aggression within and between groups. A higher number of aggressive incidents were significantly associated with a higher number of coercive measures. Conclusions: The findings have implications for the understanding of how group climate may play a role in reducing aggressive incidents at the living group in treatment of individuals with MID-BIF in secure forensic settings.