Two greenhouse experiments were carried out to analyze the shoot sodium (Na ⁺ ) partitioning, yield, and fruit quality of ‘Cuore di Bue’, a salt-sensitive heirloom tomato ( Solanum lycopersicum L.), ungrafted or grafted onto interspecific tomato hybrid rootstocks ( S. lycopersicum × S. habrochaites ) ‘Maxifort’ and ‘Arnold’ in 2009, ‘Arnold’ and ‘Armstrong’ in 2010, grown at different salinity stress (SS) levels (0, 20, and 40 m m of NaCl in 2009; 0 and 20 m m of NaCl in 2010). In both experiments, an interaction was observed between grafting combinations and SS levels in terms of fruit yield, and fruit juice Na ⁺ content. Under no SS conditions, plant grafted onto ‘Maxifort’ and ‘Armstrong’ provided the highest yield in 2009 and 2010 experiments, respectively. In the presence of 20 m m of NaCl, plants grafted onto ‘Arnold’ provided a marketable yield 23.5% (on average) higher than plants grafted onto ‘Maxifort’ or ungrafted in 2009 and 33% (on average) higher than plants grafted onto ‘Armstrong’ or ungrafted in 2010. The further increase of SS to 40 m m of NaCl considerably reduced the productivity of all grafting combinations. At 20 m m of NaCl, plants grafted onto ‘Arnold’ showed also a higher capacity to modulate shoot Na ⁺ partitioning with respect to ungrafted plants by increasing Na ⁺ accumulation in older leaves (52%) and reducing Na ⁺ content in younger and most active leaves (24%), thus enabling the maintenance of higher K ⁺ /Na ⁺ , Ca ²⁺ /Na ⁺ , and Mg ²⁺ /Na ⁺ ratios compared with ungrafted plants. Fruit total soluble solids content, titratable acidity, and dry matter were unaffected by grafting at any SS level, whereas under SS, the fruit juice Na ⁺ content of grafted plants was consistently lower (from 19% up to 68%) than that of ungrafted plants. Under moderate SS conditions (20 m m of NaCl), the use of rootstock genotypes such as ‘Arnold’ having a particular ability to reduce Na ⁺ accumulation in younger and most active leaves may increase tomato yield and enhance tomato nutritional value by reducing the fruit juice Na ⁺ content.