Social innovations are discussed as solutions to societal challenges, such as ensuring quality healthcare provision. Co-creation (i.e. the collaboration of actors who share their knowledge and skills), a primary feature of social innovation, can play a central role in changing formal institutions such as regulations, which is crucial to solving challenges in highly regulated sectors such as healthcare. However, research investigating how co-creation in social innovation can influence regulations is lacking. We investigate how co-creation can affect the ways social innovation actors influence healthcare regulations by analysing three social innovations in the Bernese Oberland, a Swiss mountain region facing the challenge of maintaining quality healthcare provision. Applying innovation biographies and semi-structured interviews, we find that two co-creating actor types were involved in influencing regulations: social innovation leaders and actors who fulfil central social innovation tasks. They influenced regulations by suggesting changes and inducing others to implement them, and they learned knowledge and skills in co-creation that helped them perform these activities. However, resources unrelated to co-creation also helped them influence regulations, such as actor networks and skills in persuading others. Co-creation in social innovation can thus support institutional change but is not a guarantee for it.