Two extra days are being added to the Leaving Certificate written exams schedule.
The change is being introduced from next June in an attempt to ease pressure on students.
A small but significant number of students studying minority subjects have experienced timetable clashes in previous years.
This has meant that some students have been forced to sit three Leaving Certificate examinations in the same day.
It is hoped that the changes announced today will minimise such subject clashes.
The Leaving Certificate examinations currently run over a 13-day period, starting on the Wednesday after the June bank holiday.
The addition of two more days brings the total examination period to 15 days.
Announcing the change, Minister for Education Joe McHugh said he was confident that the small number of students who may have to sit three examinations in a single day will be significantly reduced as a result of these changes.
"The change is about trying to ease pressure. From talking to Leaving Cert students I hear how the exams play on their minds and any changes that we can make to ease that are really welcome," he said.
"The State Examinations Commission will also continue to be mindful of changes in students’ subject choices and how the exams and the timetable should be set to minimise clashes and limit unnecessary stress."
The State Examinations Commission has published the Leaving Certificate timetable for 2019 which is available here