On Wednesday, Kelly Grove Racing confirmed the veteran will link up with Reynolds in the #26 Penrite Racing Ford Mustang.
October's Repco Bathurst 1000 will be Youlden's 21st attempt at the Great Race.
He will also race in the Porsche Carrera Cup this year, allowing him to stay match fit leading to the sole enduro of the upcoming Supercars season.
The Kelly squad will also field Youlden at its passenger ride events throughout 2021 to give him the opportunity to adapt to the Mustang.
He will get his first taste of the Penrite Racing entry at the team's corporate ride event at Phillip Island on Wednesday.
"I'm really excited to be joining Dave and the team at Penrite Racing for Bathurst this year," Youlden said.
"It's an interesting and exciting time to be joining the team, there's obviously been a lot of change at Kelly Grove Racing which seems to be extremely positive and the team is really ambitious.
"Winning Bathurst with Dave in 2017 was one of the highlights of my career, it's something that I'll never forget so obviously I'm really looking forward to giving it another crack this year after watching from the sidelines in 2020.”
"Myself and Dave obviously have history, we know how each other work and I'm used to driving the car the way that Dave has it setup so I think we'll be able to gel together really well and hopefully have a strong result.
"We definitely have experience on our side, together we'll probably be one of the most experienced combinations that'll race at Bathurst which is cool."
"We've got the dream team back together and it feels awesome," Reynolds said.
"Myself and Luke shared some great memories together when we won the Bathurst 1000 in 2017, which is still one of the greatest moments of my life.
"I've enjoyed driving with him and he's a great guy so it was only right we recruit him for Bathurst again this year.
“Luke will be doing quite a lot of racing this year which is great for him and it means we know he'll be race ready when it comes time to get in the car for Bathurst.
"With how good the co-driver field is these days it's hard to turn up having not raced all year and give it a crack so with his regular Porsche meetings I think he'll turn up confident and raring to go."