Objectives: To explore the experiences of older adults who participated in a randomised controlled trial (RCT) that tested cognitive behaviour therapy for insomnia and depression. Methods: Focus groups were conducted post treatment for older adults (M age = 75 years; 61% female) who participated in a RCT that tested two experiential interventions targeting comorbid insomnia and depression (cognitive behaviour therapy for insomnia, CBT-I; cognitive behaviour therapy for insomnia plus positive mood strategies, CBT-I+). Six semi-structured focus group interviews (N = 31) were analysed using a qualitative thematic analysis. Results: Interview data were transcribed into 424 sentences and 60 codes were extracted. Thirty-four initial themes emerged, which were transformed into 3 themes and 10 subthemes. The three primary themes were (1) positive experiences, (2) negative experiences, and (3) suggested modifications. The positive subthemes were (1a) therapists, (1b) togetherness, (1c) use of strategies reduced symptoms, and (1d) acceptance. The negative subthemes were (2a) persistent symptoms, (2b) program too condensed, and (2c) attendance obstacles. The suggested modifications were (3a) lengthen program, (3b) multi-dimensional learning, and (3c) multi-modal delivery options. Conclusion: The experiences and suggestions identified in this study strengthen the foundation to advance therapeutic program development for older adults with comorbid insomnia and depression. Future CBT-I programs for older adults may be improved by increasing the length of therapy (e.g. 8 sessions to 12 sessions), adding multi-dimensional learning opportunities (e.g. visual/audio/mentorship), and offering various modes of treatment delivery (e.g. group, individual, internet, telephone).