The goalkeeper has been with Albion for over a decade and was third choice behind Jason Steele and Bart Verbruggen last season.
McGill said: “It was an easy decision for me after a couple of conversations with the gaffer, I got told you can play with freedom, within the realms of what we’re trying to do here, and that’s all any player wants to hear really.
“For me, having a run of games, having the freedom to play under a gaffer that plays a similar style to what I’m used to, that’s all I’m after, winning and success with a team that deserves it I think.”
Dons boss Mike Williamson added: “We ask a lot of our goalkeepers, and that’ll be no different for Tom. He’s a bright, energetic player who we’re confident has the footballing intelligence to excel in our system. Brighton have done a fantastic job with his development, now it’s up to us to get the best out of him.”
