While some services were held under tight security, some came at a time of political unease.
In the wake of President Mohamed Morsi's removal from power, the threat of violence towards Coptic Christians has intensified.
This religious festival has also promised hope.
Liberal New Wafd party leader Sayed Badawi said the celebration was joyous.
"We are on the verge of voting on a constitution that reserves the right of national unity and we have come here today to join our brothers and sisters in their Christmas celebrations, and I hope each year Egypt remains good and well," he said.
Around the world, services to mark Orthodox Christmas were held by Christian denominations that follow the Julian calendar.
In Russia, President Vladimir Putin attended a service in the new cathedral in Sochi built in time for the Winter Olympics.
Watch the full report in the video player above.