He takes over from the now departed Anthony Barry.
John Eustace has been appointed as Republic of Ireland assistant coach.
The Englishman joins Stephen Kenny's staff as a replacement for Anthony Barry, who departed last month.
Eustace is currently assistant manager with Championship club QPR, and will combine that job with his new role.
Ireland are due to train later today as they begin preparations for Saturday's friendly against Belgium.
John Eustace said:
"I'm delighted to join the Republic of Ireland coaching staff and excited to link up with the squad this week for the matches against Belgium and Lithuania.
The opportunity to join Stephen Kenny's coaching staff is an exciting prospect and I'm looking forward to working with this young group of players.”
Republic of Ireland manager Stephen Kenny said:
“John has been assistant manager with Queens Park Rangers for four years and has established himself as an accomplished and well-respected coach.
He is an excellent addition to the coaching team and we’re looking forward to linking up for the two matches against Belgium and Lithuania, and for the season ahead.”
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