As conventional cropping systems face deterioration of soil quality, loss of biodiversity, and declining ecosystem services, there is an urgent need to change practices to more sustainable yet productive systems. Intercropping enhances biodiversity, maximizes land productivity, and optimizes biogeochemical cycles in agroecosystems, but is lacking acceptance from European farmers. Legume-based intercropping takes advantage of biological diversity and synergistic effects between companion plants while reducing external inputs. A major objective of LEGUMINOSE is to identify the obstacles to intercropping and enhance farmers’ acceptance by providing knowledge and demonstrations that promote economic, environmental, and social benefits of legume-cereal intercropping. LEGUMINOSE will assess intercropping potential by focusing on pesticide reduction, plant-microbe mediated element cycling, soil health improvement, and crop quality and health. To overcome barriers to intercropping implementation, we will establish a network of six field trials and farm labs (20 farms in each country; 180 on-farm trials) in different pedo-climatic zones across Europe (IT, DE, DR, ES, PL, CZ, UK), Egypt, and Pakistan. Furthermore, we will integrate remote sensing and crop modelling to survey fields, upscale the field-scale results, and create a web-based decision support system on intercropping. In collaboration with various stakeholders, legume-intercropping systems' economical, ecological, and social gains will be assessed and disseminated with international outreach from farm-level to policymakers. We will recognize and involve the whole value chain to explore and test innovative marketing strategies for the products of intercropping. LEGUMINOSE will contribute to the ecological intensification of European agriculture by providing science-based, farmer-led, and economically viable transformations for legume-based intercropping systems.