An image sensor includes a substrate including a first surface and a second surface, a first device isolation layer disposed in the substrate and defining a plurality of pixels in the substrate, and having a lower surface adjacent the first surface of the substrate and an upper surface adjacent the second surface of the substrate. Each of the pixels includes a photoelectric conversion element, a floating diffusion region adjacent the first surface of the substrate, and a grid pattern on the second surface of the substrate. At least one of the grid patterns is not vertically aligned with the first device isolation layer.