Genetic algorithms (GAs) have proved to be a powerful tool in cryptography. The standard advanced standard encryption (AES) algorithm incurs high computation costs and has problems in pattern formation when applied to image encryption. It is also prone to the differential and side channel attacks. In this paper, a modification of AES has been proposed for high-definition (HD) Image Encryption that uses a genetic approach for the S − Box Generation and Key Expansion processes. S − Boxes have been evolved to have high non-linearity and low transparency. Also, in the key generation, the process has been randomised by using only genetic operators. As a result of applying genetic modifications to AES, the proposed algorithm has been found to be more secure against the differential and side-channel attacks and shows reduced pattern appearance when applied for encryption of HD images. Copyright © 2018 Inderscience Enterprises Ltd.