El-Sisi took the oath of office Saturday before parliament amid tight security enforced throughout Cairo.
His only challenger in the March election was a little-known politician who supported him, after several more serious potential candidates were either arrested or intimidated into dropping out.
El-Sisi led the 2013 military overthrow of Egypt’s first freely elected president, Muhammad Mursi, amid mass protests against his divisive rule.
Since then, authorities have waged a sweeping crackdown on dissent, jailing thousands of Islamists as well as prominent secular activists. Unauthorized protests have been banned, and hundreds of websites, including those of rights groups and independent media, have been blocked.