An imaging device may include regions of active pixels, which are included in the generation of a photoelectric signal, and dummy pixels, which are not included in the generation of a photoelectric signal. Electrical characteristics of the dummy pixels may affect the photoelectric signal produced by the active pixels unless isolation is provided to reduce the electrical conductivity therebetween. An image sensor includes a substrate including an active pixel region and a dummy pixel region, a pixel isolation structure at least partially penetrating the substrate and configured to reduce electrical conductivity between an active pixel in the active pixel region and a dummy pixel in the dummy pixel region, and a dummy isolation structure at least partially penetrating the substrate of the dummy pixel region.