An image sensor includes: a substrate including an active region and a peripheral region, unit pixels disposed on the active region, device isolation patterns defining the unit pixels disposed on the active region, a light-shield layer on the substrate and having a grid structure defining optical transmission regions, color filters on the light-shield layer, and microlenses on the color filters. The device isolation patterns include first device isolation patterns and a second device isolation pattern, wherein the first device isolation patterns are disposed on a central portion of the active region, and the second device isolation pattern is between the first device isolation patterns and the peripheral region. The first device isolation patterns have a first top surface substantially parallel to a bottom surface of the substrate. The second device isolation pattern has a second top surface, wherein the second top surface approaches the bottom surface of the substrate in a direction toward the peripheral region.