In Brazil. most Eucalyptus plantations are located in regions experiencing periods of water shortage where fertilizers such as potassium (K) are intensively used to achieve high productivity. Recently. sodium(, a) has also been considered a potential nutrient. As well as tree growth, wood properties are also an important factor to consider in order to measure the impacts of silvicultural practices and water deficit on forest productivity, since they are determinants for quality and yield of pulp and paper. In a split-plot experimental design with 4-year-old Eucalyptus grandis trees, located in Sao Paulo State, Brazil, we evaluate the effects or K and Na supply compared with a control treatment under two water supply regimes (37% throughfall reduction versus no throughfall reduction) on stem volume, heartwood proportion. basic density, fiber, and vessel properties. K and Na fertilization increased stem volume 2. 7 and 1.9 fold. respectively, with a nonsignificant effect of 37% throughfall reduction. Na fertilization was more detrimental to wood properties that K fertilization, affecting heartwood proportion, basic density, and fiber wall thickness. K fertilization affected only heartwood proportion and basic density. The 37% throughfall reduction only affected wood basic density. increasing it. Effects of fertilization treatments did not change regardless changes in water supply.Despite the detrimental effects of fertilizers (stronger with Na supply) in wood properties there is a large beneficial effect on stem volume (stronger with K supply), even under a water availability reduction, that would be compensates the loss of wood quality for pulp and paper production.