OBJECTIVE: Rheumatoid arthritis (RA) is a chronic autoimmune disease, with a prevalence of insomnia disorders in up to 70%. Patients' experiences of participating in group-based cognitive behavioural therapy for insomnia (CBT-I) are sparsely explored, and CBT-I has not been evaluated in patients with RA until now. Therefore, the aim was to explore patients' experiences of CBT-I and how the components of CBT-I were incorporated in sleep management. DESIGN: We conducted a qualitative study with semi-structured interviews. The interview guide was developed based on CBT-I, with questions that explicitly explored the participants' experiences of sleep education and the behavioural components of CBT-I. SETTING: Interviews were conducted one-to-one at Center for Rheumatology and Spine Diseases, Copenhagen. PARTICIPANTS: Patients with RA who had received CBT-I as intervention in a randomised controlled trial (N=11). The analysis was based on a reflexive thematic method. RESULTS: Five themes were identified (1) When knowledge contributes to an altered perception of sleep, referring to the reduced misperception and increased motivation that followed sleep education, (2) Overcoming habits and perceptions to accelerate sleep onset, referring to barriers related to sleep behaviour and how stimulus control enabled them to find meaningful behaviour, (3) The sleep window of challenges in learning how to sleep right referring to that payoff from sleep restriction did not come easily or by magic, and commitment gave them confidence to continue, (4) Relaxation becomes a behavioural habit and goes beyond sleep, referring to a means to achieve a relaxed body and mind and how they thereby coped better with RA-related symptoms and (5) Break the cycle and regain control referring to how trust in one's own accomplishment was crucial to reducing worrying. CONCLUSION: The process towards eliminating insomnia was a bodily experience and involved a changed mindset that resulted in an alteration of behaviour and cognitions.