RATIONALE: People living with both chronic obstructive pulmonary disease (COPD) and frailty have high potential to benefit from pulmonary rehabilitation but face challenges completing programmes. However, research to understand ways to optimise participation in this group is lacking. OBJECTIVE: To explore the experiences, needs and preferences of people with COPD and frailty referred for out-patient pulmonary rehabilitation. METHODS: Semi-structured interviews with people with COPD and physical frailty, purposively sampled by age, living status, level of frailty, and completion of pulmonary rehabilitation. Thematic analysis with a critical realist perspective was used, involving relevant stakeholders with clinical, academic and lived experience for interpretive rigour. RESULTS: 19 people with COPD and frailty were interviewed, with a median age of 78 years (range 58-88). Nine did not complete their pulmonary rehabilitation programme. Four themes were identified: striving to adapt to multidimensional loss, tensions of balancing support with independence, pulmonary rehabilitation as a challenge worth facing, and overcoming unpredictable disruptions to participation. Participants described constantly adapting to their changing health and resulting multidimensional losses (e.g. functional abilities, relationships, confidence). This involved traversing between independence and seeking support, set against a mismatch between their needs and what support is available. People with COPD and frailty can be highly motivated to participate in pulmonary rehabilitation, despite the physical and mental demands it entails, and report a range of benefits. Yet in the context of changeable health, they must often overcome multiple unpredictable disruptions to completing rehabilitation programmes. Participant determination and flexibility of services can facilitate ongoing attendance, but for some, these unpredictable disruptions erode their motivation to attend. CONCLUSIONS: People with COPD and frailty experience accumulating, multi-dimensional loss. This group are motivated to complete pulmonary rehabilitation but often require additional support and flexibility due to fluctuating and unpredictable health. Person-centred approaches should be considered to minimise disruptive health events and support pulmonary rehabilitation participation and completion. Service adaptations could allow more flexibility to meet the changing needs of this group and enable communication around how pulmonary rehabilitation might align with their priorities.