Egyptians living abroad will finish voting on the country's new constitution on Monday at 8 p.m. (local time of each country).
Polls were supposed to close on Saturday but the judicial committee that is overseeing the referendum decided to extend the vote to allow those who live outside major cities to mail their ballots.
Between six and eight million Egyptians live abroad, mostly in Europe, North America and the Arab Gulf region, according to official reports.
By Saturday, 180, 000 Egyptian expatriates had voted, with Kuwait concurring first place.
The counting of ballots will take place immediately after polls close in order to conclude before December 20.
Local polls were conducted on Saturday in the first round of the referendum on a draft constitution written by an Islamist-dominated assembly, while the second round is scheduled for December 22.