The 42-year-old, who moved to the DW Stadium from Rotherham in 2005, replaces Phil Hughes in the role
Pollitt made 52 appearances for Latics during his nine seasons with the club and he is delighted to be staying on after hanging up his gloves.
He told the club's official website: "I had offers to keep playing. But really to have an opportunity to begin my coaching career at a top Championship club, working with international goalkeepers, was too good a chance to miss and I'm delighted that the gaffer has shown such faith in me.
"It's going to be a bit strange at first, changing in a different dressing room and having to coach former team-mates, but it's something I will have to get used to quickly, having MP on my top rather than the number 12!
"This is the next stage of my career and I am fortunate to be given the chance.
"I've been in the game 25 years, worked under so many different coaches and I'm looking forward to being able to put that experience into use in creating my own training sessions.
"On top of that I'm finishing off my coaching badges and this is an amazing opportunity for me at a club I know so well and have been very happy at. I can't wait to get started."