Endoplasmic reticulum stress has been reported to be involved in the pathogenesis of retinitis pigmentosa, macular degeneration and diabetic retinopathy. In the present study, we examined the effects of deferiprone, an iron chelator, on photoreceptor degeneration induced by tunicamycin (300 nmol/eye), an endoplasmic reticulum stress inducer, in the rat retina. Scotopic electroretinogram measurement and morphometric evaluation were done 7 d after the injection of tunicamycin. In the scotopic electroretinogram, intravitreal deferiprone (5 nmol/eye) injected simultaneously with tunicamycin significantly reduced the decreases in a- and b-wave amplitudes induced by tunicamycin. Morphometric evaluation showed that deferiprone significantly reduced thinning of the outer nuclear layer, the inner segment and the outer segment. These results suggest that iron chelation therapy may be a good candidate for the treatment of eye diseases related to endoplasmic reticulum stress.