During the 20th century, agriculture experienced major gains in productivity via homogenization and intensive use of inputs. This model is jeopardized by the awareness of rapid global change, in particular climate change, and the need for greater agricultural sustainability. Crop genetic diversity should play an essential role in this context, as it could promote various ecosystem services essential for adaptation to climate change. Increasing within field diversity through the use of cultivar mixtures is a timely option, testified by with some significant “success stories” in the past. Despite the abundant bibliography demonstrating the interest of intra-specific crop diversity, cultivar mixtures are poorly developed worldwide. In this context, the WHEATAMIX project studies the interest of mixing wheat genotypes to reinforce the sustainability and resilience of agricultural production and the provision of various ecosystem services. Based on a highly multidisciplinary approach we analyze the interactions among genotypes and with the environment, to develop new methods for breeding and/or combining wheat varieties to obtain performing blends in a global change context. Complementary experimental approaches are being deployed: i) a main diversity experiment (Eighty- eight wheat plots with 1, 2, 4 or 8 varieties, under low input) to quantify over several years the variety diversity effects on ecosystem services; ii) replicates of the same diversity experiment in 4 sites across France, to test the robustness of wheat diversity effects under a wide range of soil and climate conditions; iii) a network of 50 farms, encompassing agro-climatic variability in the Paris basin, to compare the ecological and techno-economic performance of blends with that of monocultures, using direct links with key stakeholders. The first results provide a comprehensive characterization of the multiple ecosystem services provided by genetic diversity (yield stability; regulation of foliar diseases; insect pest and weed biocontrol; maintenance of soil fertility; biodiversity conservation), and the trade-offs and synergies that exist among ecosystem services. The result also guide the selection of variety mixtures and corresponding bundles of functional traits that can deliver particular groups of services to tackle the climate change issue.