A back-illuminated image sensor may include a substrate in which photodiodes are disposed; an insulating layer on a first surface of the substrate; an interconnection layer in the insulating layer; an anti-reflection layer between the substrate and the insulating layer; a plurality of color filters on a second surface of the substrate opposite to the first surface; and a microlens on the color filters. Because the anti-reflection layer may be between the substrate and an interlayer dielectric layer, the reflection rate of light that passes through the substrate and arrives at an interface between the substrate and the interlayer insulating layer may be reduced.