Charlie Flanagan said he was "disappointed and frustrated by a further adjournment"
Ibrahim Halawa's trial in Egypt has been delayed for the 20th time.
Mr Halawa, from Firhouse in Dublin, has been held in an Egyptian jail since his arrest during demonstrations against the ousting of president Mohammed Morsi in August 2013.
The 21-year-old has now spent 1,313 days in prison without trial.
He faces trial alongside 493 other defendants, and the next hearing is scheduled for April 5th.
Colm O'Gorman of Amnesty International said: “This young Irish citizen has been through a horrific experience. He’s been imprisoned without trial for almost four years and endured 20 trial delays. As Ibrahim spends his 1,313th night unjustly incarcerated, Amnesty International continues to be gravely concerned for his mental and physical wellbeing.
"We reiterate our call on the Egyptian authorities to drop all charges against Ibrahim and to order his immediate and unconditional release."
Foreign Affairs Minister Charlie Flanagan said in a statement: "I am disappointed and frustrated by a further adjournment in the court case in which Ibrahim Halawa is a defendant.
"This is a source of great concern to the Irish government."
He added he was concerned "at persistent reports that Ibrahim is on hunger strike. I urge him in the strongest possible terms not to pursue such a course of action, and to protect his health in every possible way."
The Taoiseach earlier said he is “disturbed” by reports on the deteriorating health of Mr Halawa.