Grafting with different rootstocks may provide increased tolerance and yield, even under poor-quality irrigation conditions. We examined the effects of potato rootstock on physiology, dry mass, and yield of tomato scion in pots irrigated with saline water. Tomato (cv. Ikram), potato (cv. Charlotte) and grafted (cv. Ikram/Charlotte) plants were subjected to saline and non-saline water-irrigation treatments (electrical conductivity 5.0 and 1.0 dS m−1, respectively). Physiological, mineral, dry mass and yield analyses were performed. Potato rootstock unchanged the total plant dry mass without disturbing the physiology of the tomato scion under saline water irrigation. The grafted plants showed differential root trait responses with balanced mineral partitioning across plant parts under saline water irrigation. Grafted plants were superior in water productivity by 56.8 and 70.5 % over the control plants under saline and non-saline water-irrigations, respectively. Potato rootstock could improve the tolerance of tomato scion to saline water irrigation through distinct changes in dry mass allocation, and the induction of mineral-compartmentalization processes. The results of this study suggest that the use of potato rootstock may be a good strategy for increasing tolerance to saline water irrigation, as well as the production of both fruits and tubers in a single plant. © 2021 The Author(s)