MK Dons manager Paul Ince swooped for Carrington after he impressed in a trial and he also caught the eye last season when Carrington played his part in Crewe's 2-2 draw at the Stadium MK.
Carrington signed professional forms back in 2006 and made 37 appearances in total for the Railwaymen during his time at the club. He was released at the end of last season following releagtion to League Two, his release was a suprise for many a Crewe fan as many thought he would of done a job in League Two.
MK Dons assistant manager Karl Robinson told the MK Dons official site "Mark is only 22 but he has fantastic potential and is someone we see as being able to take the Club forward. His dedication and willingness to succeed are parallel to the Club's ambition, he's full of energy and is a very talented footballer."
Last season Carrington made 37 appearances netting two goals with them coming against in the 2-1 win over Tranmere and ironically in the 2-2 draw with MK Dons.