The trial of Ibrahim Halawa has been postponed until early March.
The 20-year-old Irishman is being tried alongside more than 490 other people.
Mr Halawa was arrested by the Egyptian army as he took refuge in a Cairo mosque while Muslim Brotherhood protesters staged a "day of rage" outside in August 2013.
Mr Halawa faces a possible death penalty and has been imprisoned for more than 28 months without trial.
Minister for Foreign Affairs Charlie Flanagan has said that the adjournment is "a matter of serious concern for all of us". He said Ireland's ambassador in Egypt attended court today and spoke with members of Mr Halawa's family.
The minister said the Department of Foreign Affairs is maintaining close and regular contact with Mr Halawa, as well as his family and Egyptian team.
Meanwhile, Amnesty International has said it remains concerned for Mr Halawa's well being, and it has reiterated its call for his release.
It is the twelfth time legal proceedings have been adjournment since 2013.