Reid enjoyed a playing career with the club spanning 10 years across two different spells, making his breakthrough in professional football at The City Ground before returning in 2011.
The former Republic of Ireland international made 290 appearances in the Garibaldi before making the transition into coaching, being named the head coach of the Republic of Ireland Under 18s side at the start of 2019.
Reid will split his time between Forest and the FAI, joining The Reds on a casual basis as part of a restructuring of the Under 23s coaching set-up.
Jimmy Gilligan has left his role as Under 23s head coach, departing for a new role at The FA, with Chris Cohen stepping up to take on the position and bringing in former teammate Reid to assist him.
The club would like to thank Jimmy for his efforts at the club and wish Chris and Andy the best of luck in their new roles.