Background: Caring for a child with intellectual disability can be stressful. No data on the longer-term effects of cognitive-behavioural treatment (CBT) on parents from a Chinese-speaking background who have children with intellectual disabilities are available in the literature. This study attempted to fill this research gap by examining the maintenance effect of CBT among the Chinese parents of such children in Melbourne, Australia. Method: Thirty-nine participants took part in our CBT groups and attended follow-up meetings. A questionnaire comprising four instruments, the Parenting Stress Index (PS)--Parent Domain, General Health Questionnaire-12 (GHQ-12), Abbreviated Quality of Life Enjoyment and Satisfaction Questionnaire (Q-LES-Q-18) and Dysfunctional Attitude Scale (DAS), was administered to the participants at the pre- and post-test stage and at the 6-month follow-up. Results: One-way repeated-measures analyses of variance revealed significant time and group effects in the PS (F[subscript 2,27] = 16.93,P less than 0.001), Q-LES-Q-18 (F[subscript 2,27] = 15.98, P less than 0.001), GHQ-12 (F[subscript 2,27] = 81.93, P less than 0.001) and DAS (F[subscript 2,27] = 15.50, P less than 0.001) scores at the three measurement times. The participants continued to maintain significant improvements in mental health and quality of life and declines in the severity of parenting stress and dysfunctional attitudes at the 6-month follow-up. Effect size analyses revealed mostly large differences in the foregoing measurements (Cohen's d = 0.76-2.18) between the pre-test and 6-month follow-up. Employing a cut-off score of 3/4 in the GHQ-12 to identify at-risk and not-at-risk cases, approximately 90.5% of the participants could be classified as not-at-risk at the follow-up. Lastly, regression analyses showed that changes in DAS scores significantly predicted changes in the GHQ-12 and Q-LES-Q-18 scores at the follow-up. Conclusions: This study provides preliminary evidence of the 6-month maintenance effect of CBT groups for the Melbourne-resident Chinese parents of children with intellectual disabilities.