Former Republic of Ireland internationals Damien Duff, Keith Andrews and Alan Kelly will join new manager Stephen Kenny's backroom staff.
Kenny, 48, replaced Mick McCarthy at the helm after Euro 2020 was postponed because of the coronavirus pandemic.
Meanwhile, Jim Crawford succeeds Kenny as the Republic's Under-21 manager.
Ex-Chelsea, Newcastle and Fulham winger Duff will join on 1 August, having spent the last year on the coaching staff of Scottish champions Celtic.
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Andrews had previously assisted Kenny in the U21 set-up, while Kelly will continue as goalkeeping coach.
Former Manchester United and Sunderland defender John O'Shea comes in to assist Crawford with the Under-21s, having previously been part of the Reading backroom team.
The new-look coaching staff comes after the Football Association of Ireland chose to accelerate its managerial succession process because of the indefinite postponement of the Republic's upcoming Euro 2020 play-off.
Kenny, 48, was set to replace McCarthy at the end of this summer's tournament before the virus led to the delay of the competition.