Background: In secure residential facilities, group climate perceptions of clients with mild intellectual disability or borderline intellectual functioning are systematically assessed for quality improvement. A valid and reliable measure may ensure that this process is consistent. The Group Climate Inventory--Revised (GCI-R) is a new measure to assess group climate perceptions. Method: Confirmatory factor analysis was conducted in 148 adult clients (79% male) with mild intellectual disability or borderline intellectual functioning in a secure facility to examine internal structure validity and internal consistency reliability of the GCI-R. Results: The results indicate support for the five-factor structure of the GCI-R ('Support', 'Growth', 'Repression', 'Peer interactions', and 'Physical environment'). The internal consistency reliability of its scales ranged from acceptable to good ([alpha]: 0.72-0.87; [omega]: 0.76-0.86). Conclusion: The GCI-R demonstrates evidence of psychometric adequacy when applied to adult clients with mild intellectual disability or borderline intellectual functioning in secure residential facilities.