Background: Physical activity has numerous health and well-being benefits for older adults, but many older adults are inactive. Interventions designed to increase physical activity in older adults have typically only produced small effects and have not achieved long-term changes. There is increasing interest in participatory approaches to promoting physical activity, such as co-production, co-design and place-based approaches, but they have typically involved researchers as participants. This study aimed to understand the experiences of decision-makers and service developers with the introduction of such participatory approaches when developing new physical activity programmes outside of a research setting. Methods: Semi-structured, qualitative interviews were conducted with 20 individuals who were involved in commissioning or developing the Greater Manchester Active Ageing Programme. This programme involved funding eight local authorities within Greater Manchester, England, to produce physical activity projects for older adults, involving participatory approaches. An inductive thematic analysis was conducted, structured using the Framework approach. Results: Interviewees identified important benefits of the participatory approaches. The increased involvement of older adults led to older adults contributing valuable ideas, becoming involved in and taking ownership of projects. Interviewees identified the need to move away from traditional emphases on increasing physical activity to improve health, towards focussing on social and fun elements. The accessibility of the session location and information was considered important. Challenges were also identified. In particular, it was recognised that the new approaches require significant time investment to do well, as trusting relationships with older adults and partner organisations need to be developed. Ensuring the sustainability of projects in the context of short-term funding cycles was a concern. Conclusions: Incorporating participatory approaches was perceived to yield important benefits. Interviewees highlighted that to ensure success, sufficient time needs to be provided to develop good working relationships with older adults and partner organisations. They also emphasised that sufficient funding to ensure adequate staffing and the sustainability of projects is required to allow benefits to be gained. Importantly, the implementation of these approaches appears feasible across a range of local authorities.