Nigel Pearson's side celebrated a fourth win in five matches thanks to goals in each half from David Nugent and the manager's son James Pearson.
Having won the Championship title last term. Leicester have added six new players to their squad ahead of their return to the top flight.
However, it was an old face who set them on their way midway through the first half at Stadium MK.
After a scrappy start, it was Nugent who broke the deadlock, with the aid of a deflection, from the edge of the penalty area in the 24th minute.
Jeffrey Schlupp produced some neat work on the wing before finding Nugent in space.
Dons keeper David Martin looked to have his effort covered until it clipped a defender and flew into the opposite corner.
Leicester could have doubled their lead soon after as Riyad Mahrez met a cross from one of their new signings, Marc Albrighton, but the Algeria international placed his header wide of goal at the back post.
League One Dons nearly caught their visitors off guard in the final minute of the half when highly rated youngster Dele Alli saw his low effort strike the post.
Leicester could have extended their lead shortly after the break when Mahrez's corner found Nugent unmarked inside the penalty area, but this time the striker could not keep his effort down.
Benik Afobe, playing just hours after agreeing a loan move to the Dons from Arsenal, had his only sight of goal two minutes before the hour but failed to find any quality to convert Danny Green's cross.
And the hosts were punished on 68 minutes, as Pearson latched onto a clearance before lashing a stunning long-range effort into the top corner.