Several forest management strategies can be used to cope with climatic changes. Reducing stand density and mixing tree species are two of them. Several studies investigated these strategies separately, but we do not know what the outcome would be if we used them conjointly. The main objective of our study was to quantify tree species interactions effects on radial growth during a water stress period and to determine whether these effects changed with different levels of competition (different levels of stand density). This study was based on a long term triplet experiment (OPTMix) made of pure and mixed stands of mature Quercus petraea and Pinus sylvestris in Orleans’ forest (Central France). In this experiment, there are three repetitions of two densities (low and medium) in each composition (pure oak, mixed stands, pure pine). We followed radial growth of trees through 270 manual dendrometers spread over 21 plots. In each plot, the microclimate was monitored, and soil moisture sensors were set up at several soil depths in order to follow the drought. We found that the mixture had no effect on oak growth, but a small negative effect on pines when there was a water stress during the summer. Investigations are still in progress to determine if this result depends on stand density. Reducing stand density and the mixing of tree species are promising strategies, but understanding their combining effects still require further research.