Abstract Background In health promotion programmes (HPP), it is crucial to have intersectoral collaboration within coalitions and to build networks between health and other societal sectors. However, collaboration in coalitions and networks does not develop just because it is needed. Several factors that affect intersectoral collaboration are identified and defined as prerequisites for success in coordinated action for health in the Healthy Alliances (HALL) framework. A health broker role is recognised as being helpful in connecting the coalition with the broader network, and participatory action research is deemed supportive because it facilitates evaluation, reflection, learning, and action. Because insight into how processes that affect collaboration develop over time lack, this study aimed to provide insights into the processes that facilitate building and maintaining a coalition and its network within a HPP programme. Methods As part of participatory action research, the coordinated action checklist (CAC) and a composed network analysis (CNA) were used in 2018 and repeated in 2019. Respondents were coalition members (n = 6). The CAC and CNA results were linked back into the coalition in five group sessions and used for reflection on progress and future planning. Results Coalition governance, interaction with the context, network building and brokerage, and generating visibility emerged as the most prominent processes. Important insights concerned the health broker's role and positioning, the programme coordinator's leadership, and the importance of visibility and trust leading to investment in continuation. Conclusions The combined research instruments and group sessions supported discussion and reflection, sharing visions, and adjusting working strategies, thereby strengthening the coalition's capacity. Thus, participatory action research was useful for evaluating and simultaneously facilitating the processes that affect collaboration. Key messages Participatory action research is useful for evaluating and simultaneously facilitating the processes that affect collaboration. Besides insights into the processes that facilitate building and sustaining a coalition and its network, the yields of the collaboration became visible through participatory action research.