Nitric oxide (NO) is a key redox-active, small molecule involved in various aspects of plant growth and development. Here, we report the identification of an NO accumulation mutant noe1 (nitric oxide excess 1) in rice, the isolation of the corresponding gene and the analysis of its role in NO-mediated leaf cell death. Map-based cloning revealed that NOE1 encoded a rice catalase OsCATC. Further, noe1 resulted in an increase of hydrogen peroxide (H2O2) in the leaves, which consequently promoted NO production via activation of nitrate reductase (NR). Removal of excess NO reduced cell death in both leaves and suspension cultures derived from noe1 plants, implicating NO as an important endogenous mediator of H2O2-induced leaf cell death. Reduction of intracellular SNO (S-nitrosothiol) levels, generated by over-expression of OsGSNOR, which regulates global levels of protein S-nitrosylation, alleviated leaf cell death in noe1 plants. Thus, S-nitrosylation was also involved in light-dependent leaf cell death in noe1. Utilizing the biotin-switch assay, nanoliquid chromatography, and tandem mass spectrometry (LC/MS/MS), S-nitrosylated proteins were identified in both wild type and noe1 plants. NO targets identified only in noe1 plants included glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and thioredoxin (TRX), which have been reported to be involved in S-nitrosylation regulated cell death in animals. Collectively, our data suggest that both NO and SNOs are important mediators in the process of H2O2-induced leaf cell death in rice.