CaKR1 from pepper leaves encodes an ankyrin repeat domain zinc finger that is thought to be involved in transcriptional regulation in response to pathogens and abiotic stresses. Transgenic tomato plants expressing CaKR1 show enhanced resistance to Phytophthora infestans. In this study, we further characterized this CaKR1-overexpressing transgenic tomato line. Morphologically, the leaves of the transgenic plants were thicker than those of control plants. Overexpressed transgenic plants also produced lower levels of free oxygen radicals, such as superoxide (O2-) and hydrogen peroxide (H2O2), and showed enhanced resistance to salinity and oxidative stress. In particular, transgenic plants produced higher levels of transcripts encoding the pathogenesis-related (PR) proteins LePR1, LePR2, and LePR3, as well as oxidative stress response proteins, such as superoxide dismutase (LeSOD2) and ascorbate peroxidase (LeAPX2 and LeAPX3). These results suggest that CaKR1 is a key signaling molecule regulating plant antioxidant metabolism and defense responses.