Head Coach Dave Rennie will be assisted by Jason O'Halloran, Kenny Murray, John Dalziel and du Plessis, who has agreed a new two-year deal at Scotstoun.
The South African prop will combine his current playing duties with a new role as Assistant Coach, working closely with John Dalziel, who has replaced Jonathan Humphreys as Forwards Coach.
The tight-head will provide valuable front-row cover during this year's Rugby World Cup, with a number of props likely to be in contention for a place in their respective international squads.
The 38-year-old won two Heineken Champions Cup and three English Premiership titles during his time at Saracens.
Speaking to glasgowwarriors.org, du Plessis, said: "I'm honoured to be given the opportunity to formally move into a coaching role with Glasgow Warriors.
"I've enjoyed my time at the club and I've been helping to coach the forwards over the last few months, so it's great that I can now focus more on coaching, although I'll still be available to play during the Rugby World Cup period.
"I've enjoyed getting to know John Dalziel and I'm looking forward to helping him and the other coaches as we prepare for the new campaign."
Glasgow Warriors, Head Coach, Dave Rennie, added: "We have a young, exciting group of Scottish front-row forwards at the club next season and Petrus will work closely with them on their set-piece.
"His experience both on and off the pitch will be invaluable during the Rugby World Cup period."