There is clearly a need for research in the field of occupational health service (OHS) for applying new perspectives. Proactive collaboration is needed between the OHSs and the companies. The customers of the companies using the services should be able to safeguard themselves from the health problems caused by the work environment through proactive collaboration with the OHSs.The main purpose of this interdisciplinary study was to explore how the stakeholders reflected to create and agree on core values for future challenges in OHS, as seen from the perspectives of OHS professionals and customer companies.An action research process was conducted. This study was divided into three phases. In phase I, the data were collected from interviews and diaries of interdisciplinary occupational health professionals (n=12). A focus group that sampled the eight managers of the customer companies was also included. In phase II, a questionnaire was developed with 24 questions focusing on examining the future challenges for OHS. The questionnaire was sent to customer companies (n=116). In phase III, a scoping review was undertaken.Three categories emerged from the analysis: "Balancing complex situations" clarified the complexity regarding senior employees; "Working with a proactive approach" indicated the need for working with a new proactive approach supporting sustainable health; and "Collaborate internally and externally" showed good relationships between the customer and the OHS, which is a mutual responsibility to both the partners.The results outlined that it is necessary to take action to apply new proactive health promotions, with a focus on workplace health promotion. The results also indicated that interventions for senior employees are of importance. This study was done in collaboration with the stakeholders from the occupational health care service center and the managers from the customer companies. The use of a participatory research design, including close collaboration with the participants, allows the researchers to see the challenges.