Background: Sleep disturbance is a common complaint of patients undergoing methadone maintenance therapy (MMT). There are limited studies about the effect of different treatments on insomnia due to MMT. In this study, we evaluated the effect of cognitive-behavioral treatment for insomnia (CBTI) on sleep disorders in patients undergoing MMT.Methods: Twenty-two patients with insomnia due to MMT (aged 18-60 years) participated in this randomized double-blind clinical trial. The intervention group received CBTI from a clinical psychologist for 8 weeks, whereas the control group received behavioral placebo therapy (BPT). The duration of individual sessions was 45 minutes, which was conducted once a week. The primary outcome was sleep disturbance assessed with Pittsburgh Sleep Quality Index (PSQI). Data were analyzed using SPSS software version 19.Results: Eleven patients were assigned to each group. Two groups were matched according to demographic characteristics (age, marital status, education, and daily methadone doses). Although PSQI score was significantly reduced during weeks 5 and 8 after both interventions, there was a significant difference in intervention versus time interaction (P<0.02). The effects of CBTI versus placebo were significantly different (P<0.001). The time course was also significant (P<0.001).Conclusion: This study showed that CBTI is more effective than BPT in overall sleep quality. We recommend further studies, with a larger sample, on CBTI in patients undergoing MMT.