Demographic changes in society, with an increased proportion of senior adults combined with a decreased share of working adults and lower tax revenues, challenge the ways in which municipalities promote healthy living for seniors. To meet the needs of seniors, both today and in the future, social innovations that involve the collaborative efforts of multiple stakeholders are needed. This study aims to increase understanding of co-creation in practice, as a means to induce social innovation in municipal efforts to improve the health of senior adults. A combination of structured and semi-structured interviews was conducted with a total of 18 managers and staff involved in the development of health promotion activities in 10 Swedish municipalities. The structured part consisted of rating common patterns of health promotion development, and the answers were analysed by prevalence rates of first and second mostcommon answers. Data from the semi-structured part were thematically analysed. The results showed that the involvement of senior adults was mainly at later stages of health promotion development, often via civic organisations. Organisational factors most common for shaping cocreation strategies were having more-comprehensive ways to investigate senior adults’ needs, a dedicated health promotion department and an organisational structure that support interactions with multiple stakeholders. Co-creation with extended involvement of volunteers and acting through distributed leadership was considered crucial for the inclusion of senior adults in the development of health promotion.