AVA- Footages broadcast by Egyptian television showed al-Sisi casting ballots east the capital Cairo on the amendments which also deepen the role of the Egyptian army in the political life.
Al-Sisi said in an interview he made in 2017 that he had no intent to amend the constitution and would not run for a third term.
The official channel also confirmed the start of the voting throughout the country.
Around 61 millions of Egyptians are eligible to vote on three days in nearly 10878 electoral centers.
Egyptian expatriates on Friday started voting in the referendum.
Earlier this week, Egypt’s parliament approved a proposed constitutional amendment extending the duration of presidential terms from four to six years.
It will also allow al-Sisi to eventually run for a third term in office.
Egypt’s current constitution, ratified in 2014, allows the president to hold office for a maximum of two four-year terms.
The constitutional change, however, means al-Sisi’s second term in office -- which he secured in elections last year -- will end in 2024, after which he will be allowed to run for a third six-year term ending in 2030.