Land-use conflicts between villagers and government agencies are common under the current decentralisation of resource management in Northern Thailand. They are frequently due to deep differences in interests, objectives and perceptions of the landscape resources to be managed and their use. As the complexity of the problems to be tackled increases, there is a need to design and test effective integrated, inclusive and adaptive methods fostering the co-management of the land to improve both ecological viability and social equity. Such methods should facilitate communication and the sharing of knowledge and viewpoints leading to mutual understanding, improved trust, and the design of workable co-management plans. Companion Modelling (ComMod) is a highly interactive gaming and simulation approach relying on multi-agent systems used to better understand a complex system through the co-design and joint use of different kinds of simulation models with the field actors concerned. The co-construction of a shared representation of the issue, followed by its use to simulate and assess future scenarios, facilitates multiple stakeholders' co-ordination and negotiation processes. The presentation of ComMod main theoretical references and key methodological principles is used to characterise the original posture of the practitioner who is seen as a category of stakeholder among others. This leads to a specific type of relationship with the models developed, and the local stakeholders. The operationalisation of ComMod in a process to mitigate a land-use conflict between livestock herders and foresters in a highland village is described. Its results, ranging from fostering mutual understanding to the joint design of concrete collective action, are discussed. Based on the lessons from this case study, an analysis of the strong (trans-disciplinary knowledge integration, empowerment of marginal farmers, flexibility of the approach and its simulation tools) and weak (special skills re