A dendroclimatic study was set up in a neo-deglaciated valley of the European Alps. Chronologies of tree-ring cellulose stable isotopes (δ13C and δ18O) were analyzed. The δ18O of tree-ring cellulose was strongly driven by the δ18O of winter snowfall. The δ18O chronology explained up to 34% of the winter precipitation δ18O variability. Tree rings potentially allow the reconstruction of past winter precipitation δ18O.