An image sensor and a fabricating method thereof are provided. The image sensor includes a plurality of pixels disposed in an active region and dummy pixels disposed in a peripheral region. An interlayer dielectric layer has a first thickness in the active region and a second thickness thinner than the first thickness in the peripheral region. Color filters are disposed in the active region, and a light blocking member is disposed in the peripheral region. There is substantially no step difference between the color filters and the light blocking member.