Easter, 27, has signed a two-year contract at Stadium:mk after the two clubs agreed an undisclosed fee. He is the club's fifth summer signing following the arrivals of Dan Woodards, Jabo Ibehre, David McCracken and Stephen Gleeson.
Easter told the Dons' official website: "It feels great to be here, when you get the feeling for somewhere, like I have here, it's really exciting.
"I remember watching Paul Ince's Manchester United team as a kid and I really looked up to him, so I can't wait to start working with him.
"I've come here for promotion, it's as simple as that. That's what we should be targeting as a team and I'll be giving my all to help achieve that."
Meanwhile, Blackburn first-team coach Karl Robinson has once again teamed up with Ince at the Dons after following him to Ewood Park last summer.