Agroforestry is attracting more and more interest from grapevine growers, who expect to benefit from the climate protection provided by trees to adapt their vineyards to climate change. Indeed, the microclimate in agroforestry plots may mitigate some of the adverse effects of climate change such as heat waves, drought or frost damage due to earlier budbreak of the vines. However, trees also compete for light, water and nutriments. The net effect of agroforestry on grapevine water stress, yield and grape composition is difficult to predict. The objective of this work was to characterize the effects of trees on microclimate, light and water competition, grapevine yield and grape composition. We monitored 700 grapevine plants from 2 cultivars in 6 plots in the Restinclières agroforestry platform near Montpellier over 3 years; 543 of these plants were cultivated in agroforestry (under Pinus pinea or Sorbus domestica trees), 158 were cultivated in full sun control. Measured variables included phenology, predawn water potential, water stress indicators, yield and yield components, grape chemical analysis, as well as environmental characterisation (microclimate, soil texture). Light availability varied along north-south transects between east-west oriented tree rows (Figure 1a). Although yield was reduced in agroforestry compared to full sun control, in particular for Syrah variety, no clear pattern was discernible across the transects (figure 1b). The effect of trees on grape composition varied between years and cultivars. These results indicate complex interactions between microclimate modifications and resource competition.