Plants are exposed to all types of abiotic stresses during the process of growth and development, which could adversely affect the productivity and postharvest storage quality of plants. In the current study, the expression of SNAC4-9 and the changes of physiological parameters were analyzed in tomato seedlings under various abiotic conditions and hormone treatments. The results demonstrate that all six genes were induced by these stresses at differential induction levels and that SNAC4-9 gene expression profiles were likely to be related to the ABA, SA, and MeJA signaling pathways. In addition, all of the stress- and hormone-treated seedlings exhibited significant increases in their proline content and antioxidant enzyme activities. MDA was significantly increased in seedlings exposed to stress and decreased in hormone-treated seedlings. These data collectively suggest that SNAC4-9 might function through ABA, SA, and JA signaling pathways and the regulation of proline and antioxidant systems. This study combines molecular biology and physiology to provide valuable information for further exploring the functional roles of NAC genes in response to environmental stresses and indicates that these genes may exhibit potential for enhancing stress tolerance of transgenic tomato plants and further improving the postharvest storage quality of tomato plants.