Context: Crop-livestock integration is a theoretical ideal for sustainable agriculture. However, the number of European crop-livestock farms has decreased due to multiple factors (e.g. agricultural policies and work constraints). Crop-livestock integration beyond the farm level (e.g. through grain-manure exchanges) is a relevant option to address these limiting factors. However, this integration within farmer groups is challenging because it requires collective redesign to address organizational issues.Objective: We developed a participatory approach that includes the serious game Dynamix to support the co-design of scenarios of crop-livestock integration among farms.Methods: The approach consists of six steps: (1) initial group meeting to define the problem; (2) farmer interviews to identify motivations and collect technical and economic farm data; (3) scenario co-design meeting using the serious game Dynamix, including a spatially explicit board game and a simulation model; (4) multicriteria evaluation of these scenarios at the individual farm and group levels using the simulation model included in Dynamix; (5) group meeting to discuss the results; and (6) monitoring of selected scenario implementation. We applied this methodology with two groups of farmers in southwestern France.Results and conclusions: In the two groups, crop farmers wanted to diversify their cropping systems and use manure to improve soil quality. Livestock farmers were interested in local and non-GMO feed for their animals. The scenario they selected included i) inserting cereal-legume mixtures into crop rotations on crop farms to be sold to livestock farms and ii) transferring manure from livestock farms to crop farms. In this scenario, the predicted overall gross margin increased more for livestock farmers (median = 29.90 €/ha) than for crop farmers (median = 6.60 €/ha). Nitrogen balance management was improved: crop farmers decreased their use of mineral fertilizer by 2.8–17.4 kg/ha/year; livestock farmers decreased their feed inputs improving local feed self-sufficiency. However, farmers’ workload and management complexity increased, with 22–54 h of additional work per farmer per year. Compared to other scenarios, trade-offs between individual farm and group benefits resulted in greater local autonomy in inputs but lower autonomy in decision-making. In the two groups, discussions improved trust, which is a key ingredient for transitioning to integration beyond the farm level.Significance: Our study is the first to use a standardized participatory approach based on a serious game to support the complex issue of crop-livestock integration beyond the farm level. Applying the approach to a case-study revealed its strong potential. It can easily be scaled-out to other agricultural contexts.