The objective of this study was to evaluate several selected Cucurbita genotypes for their salt resistance in a rootstock breeding program for grafted watermelon seedling production. Specifically, changes in the relative water content (RWC), leaf area (LA), total chlorophyll content (TCC) and proline concentration (PC) of a commercial cultivar (G32 code), two promising winter squash (G12 and G13 of Cucurbita maxima Duch.) lines, six pumpkin (G3, G27, G28, G29, G30 and G31 of Cucurbita moschata Duch.) lines, and four C. maxima x C. mochata hybrids (G14, G15, G40 and G42), were investigated with a control treatment and four levels of salt stress (4, 8, 12 and 16 dS/m). In this study, Cucurbita cultivars which showed significant differences according to RWC, LA, TCC and PC at least significant difference (LSD) tests (P < 0.05) and had salinity sensitivity index (SSI) value lower than 20%, were assessed as salt tolerant genotypes. The salt tolerant genotypes were grouped with principal component analysis (PCA) in each salt level. At the end of the study, all genotypes for all characteristics were generally tolerant at 4 dS/m salinity level. The G3, G12, G13, G14, G29 and G42 genotypes were resistant at 8 dS/m salinity, while the G15, G31, G32 and G40 were the most resistant genotypes at 12 and 16 dS/m. In conclusion, the selection of more salt resistant cultivars in rootstock breeding programs should be a priority to maintain growth performance in saline environments.