An image sensor includes a substrate, a first unit pixel comprising first to fourth sub-pixels arranged in a 2 ×  2 matrix form, a first pixel isolation trench encircling the first unit pixel in a plan view, a second pixel isolation trench comprising a first portion disposed between the first and second sub-pixels, a second portion disposed between the second and third sub-pixels, a third portion disposed between the third and fourth sub-pixels, and a fourth portion disposed between the first and fourth sub-pixels, inner isolation films in the first pixel isolation trench, an isolation liner on the first pixel isolation trench, and a floating diffusion region at a center of the first unit pixel in the plan view.