The Academy graduate had been training with the Under-21s whilst considering his options, following his departure from Leicester City at the end of last season.
As part of the Academy training programme, he has also taken part in a number of first-team sessions and impressed Erik ten Hag and the coaching staff.
Evans, who has been capped 102 times by Northern Ireland, will travel to Edinburgh as part of the group to face Lyon on Wednesday. Tickets remain available for the 14:00 BST kick-off at BT Murrayfield, which is also live on MUTV.