This thesis investigates the design discipline contribution on primary care health services social innovation. To this end, the thesis has been divided in three stages: (1) desk research about design, service and service design disciplines; (2) participant observational research in Design in Practice research project at Lancaster University, where it was possible to identify the service designers approaches to create new services for British National Health System (NHS); (3) an action research to evaluate the potential of service design method by creating a new primary care health service for patients with type II diabetes, in the Brazilian context. This design project was conducted at Vila Gaucha Basic Health Unit, at Porto Alegre city, by using experience based design approach. At this stage, it was possible to make a service design intervention; to create a new primary care health service for patients with diabetes type II and to evaluate the results reached by this new service. The results shows that the design competence could contribute in different ways for the creation of new primary care health services: (1) by interpreting service value and meaning for different actors involved in its use; and (2) by translating this knowledge into a visual language understandable to all, allowing the co-creation of solution; (3) by configurating services concepts, it building a persuasive argument about how people should act in a certain situation; and (4) by including these people, whose behaviour needs to be affected, in the argument co-creation process, design makes more favourable the emergence of a social innovation. As a result of this investigation, this thesis proposes a method for designing services that focus on social innovation.