The physiological blind spot refers to a zone of functional blindness all normally sighted people have in each eye, due to an absence of photoreceptors where the optic nerve passes through the surface of the retina. Here we report that the functional size of the physiological blind spot can be shrunk through training to distinguish direction signals at the blind spot periphery. Training on twenty successive weekdays improved sensitivity to both direction and color, suggesting a generalizable benefit. Training on one blind spot, however, did not transfer to the blind spot in the untrained eye, ruling out mediation via a generic practice effect; nor could training benefits be attributed to eye movements, which were monitored to ensure stable fixation. These data suggest that training enhances the response gains of neurons with receptive fields that partially overlap, or about, the physiological blind spot, thereby enhancing sensitivity to weak signals originating primarily from within the functionally-defined region of blindness. Our results have important implications for situations where localized blindness has been acquired through damage to components of the visual system, and support proposals that these situations might be improved through perceptual training.