Mimosa pigra, an alien woody weed, invaded the Mekong River Basin since ~1970 and now covers vast floodplain areas in virtual monocultures. The prickly plants produce abundant seeds which are dispersed annually by the floods. Mimosa thus represents a burden to farming communities in Cambodia where agricultural capacities are weak. To obtain information on infestations as well as farmers’ management practices and perceptions, 81 farmers were interviewed on their fields (using questionnaires) in affected areas near Kratie municipality. Data on infestations were collected at landscape and field levels. Furthermore, villagers’ groups and key informants were interviewed (open questions). Infestations covered ~30% of the land near fields. On average farmers spent 11 days per hectare annually clearing mimosa. The weed represented a major cost, but other issues (animal pests, water shortages, lack of resources) were equally important; these may be connected to mimosa invasion. Farmers mostly expressed support for ideas to combat surrounding infestations, but support depended on experiences and assets at stake. Most were unconvinced that mimosa could be eliminated from the study site. Conceivable benefits of mimosa were regarded as insignificant. Given the currently few realistic options for significantly improving management, further research is suggested within adaptive management frameworks.