The new deal will keep the 27-year-old at Reading until the summer of 2015.
“It’s absolutely great to have signed this new contract,” he said.
“I’ve been here a long time, I’ve put in a lot of blood, sweat and tears so it wouldn’t have been right to do anything other than sign again.
“The club has got great backing, there’s a real good feel around the place, the club is only going in one direction and that’s upwards.”
“I am really pleased to have secured Adam for another three years,” Reading manager Brian McDermott said.
“I have known him for a number of years now, it seems like time has flown and he has constantly been developing into a top-class goalkeeper.
“He is a lesson to young pros about what is required to get to the top of your game. His workrate, diligence and desire are second to none and we’re delighted he’s chosen to commit to us again.”
