NecroX-5 is a derivative of cyclopentylamino carboxymethylthiazolylindole (NecroX), an inhibitor of necrosis/necroptosis. NecroX-5 has been shown to scavenge mitochondrial reactive oxygen and nitrogen species, and thus preventing necrotic cell death against various kinds of oxidative stress in several tissues, including the brain. To examine the effect of NecroX-5 on retinal degeneration (RD), RD was induced in Sprague-Dawley rats by an intraperitoneal injection of N-methyl-N-nitrosourea and in BALB/c mice by blue light-emitting diode exposure. Scotopic electroretinography recording was used to evaluate retinal function. For histological evaluation, hematoxylin and eosin staining, terminal deoxynucleotidyl transferase dUTP nick end labeling, and immunohistochemistry were performed. Electroretinography recordings showed that a-waves and b-waves were significantly reduced in both RD rats and mice, whereas the amplitudes of both waves were significantly increased in both NecroX-5-treated RD rats and mice compared with untreated RD animals. In hematoxylin and eosin staining and terminal deoxynucleotidyl transferase dUTP nick end labeling assay, the outer nuclear layer where photoreceptors reside appeared to be more preserved, and there were fewer apoptotic cells in NecroX-5-treated RD retinas than in untreated RD retinas. In addition, immunohistochemistry with antiglial fibrillary acidic protein and anti-8-hydroxy-2'-deoxyguanosine showed lower levels of retinal injury and oxidative stress in NecroX-5-treated RD retinas than in untreated RD retinas. These results indicated that NecroX-5 protects retinal neurons from experimentally induced RD, suggesting that NecroX-5 may have a potential for the treatment of RD as a medication.