A Stephen Walker brace was enough to see MK Dons progress into the Quarter-Final stages of the Papa John's Trophy.
Walker opened the scoring after he was found inside the box by Scott Fraser's perfectly weighted through ball before he making it two for the evening late in the second half.
It marks the furthest the Dons have gone in the competition since Group Stages were added to the Trophy.
MK Dons made three changes from Saturday's Emirates FA Cup tie with Andrew Surman returning from injury after he missed the clash with Burnley.
Joe Mason and Matthew Sorinola were both handed starts as they replaced Cameron Jerome and George Williams respectively.
Despite MK Dons' early dominance of the ball, it was the home side who had the first chance of the game. After Keogh defended well to deny Rose a chance on goal, Ryan Watson would fire over from the edge of the box.
The Dons had the ball in the back of the net with 15-minutes gone as Fraser played in Joe Mason, he finished first time, however, the offside flag was raised against the striker.
Fraser, who has pulling all the strings, danced his way through Northampton's defence. Having weaved his way into a shooting position, he saw his right-footed strike saved by Mithell.
The Dons dominance on the evening was soon rewarded as Stephen Walker slotted home from inside the box. It came via Fraser who broke the lines with his pass before the Middlesbrough loanee opened his body to open the scoring. 0-1.
Northampton looked for the equaliser, Hoskins found some space down the left and picked out Rose, his header hit the side netting.
Mason then got in behind Northampton's defence and despite a tight angle took on the shoot himself. Mitchell got down well to parry and then claim the rebound.
The first chance of the second half fell the way of Daniel Harvie, Sorensen picked out the Scot with his low cross, his shot curled wide of Mitchell's goal.
Almost immediately Northampton took a quick throw on the left as Korboa found his way in on goal. His first shot was blocked by Keogh, with Nicholls comfortably saving his rebound.
The next chance for Martin's side fell the way of Walker as the Dons caught Northampton on the counter. Mason's deflected pass fell the way of the goalscorer who had his volley blocked.
Cameron Jerome had the chance to double the lead after he was found in on goal Harvie, his effort was cleared off the line by Hoskins.
It was that man Jerome who caused more danger for Curle's side, his pace was on full display as he forced Bolger to foul him inside the area. Walker stepped up to the spot and calmly slotted past Mitchell to double his tally for the evening. 0-2.
The draw for the Quarter-Final stages will take place later this week.
MK Dons: Nicholls, Lewington, Keogh, Poole, Fraser (Johnson 80), Walker, Surman (Gladwin 70), Sorensen, Mason (Jerome 70), Harvie (Davies 88), Sorinola.
Subs: Fisher (GK), Jallow, Smith.
Goals: Walker (27, 83)