Intercropping of legumes can be a strategy to improve soil fertility and enhance overall productivity while reducing dependency on external inputs in intensified cropping systems. Integration of legumes in maize-based cropping systems is promoted as an agro-ecological intensification option for input-constrained smallholders in uplands of Southeast Asia, but adoption rates in the region remain low. The overall aim of this study was to assess the suitability and trade-offs of integrating ricebean in maize-based smallholder cropping systems in upland areas of Northern Laos. We conducted a researcher-managed field trial to investigate the agronomic performance of ricebean/maize intercropping, and farmer-managed trials combined with surveys (N = 97), and focus group discussions in 10 villages to understand factors influencing farmers’ decision making concerning ricebean adoption. Drought, rat infestation and crop damage by grazing livestock were identified as important constraints to the production of ricebeans. Factors facilitating adoption included improvement of soil fertility, the potentially high selling price of ricebeans and the presence of extension agents, while barriers included labour shortage, concerns about competition with maize and lack of a market outlet for the ricebean produce. We conclude that the investigated maize/ricebean intercropping system is poorly suited to the current conditions in the study area, and call for farm-based studies focusing on developing locally adapted legume intercropping systems able to perform under variable rainfall conditions. Initiatives addressing challenges related to free grazing livestock and efforts to link legume producers in remote areas to emerging markets are also needed.