Kennedy Meeks and Joel Berry II added 12 points apiece, and Theo Pinson, Isaiah Hicks had Brice Johnson each had 10 for the Tar Heels (4-1), who tumbled from their top spot in the AP poll earlier in the day after their 71-67 loss at Northern Iowa.
North Carolina will play Kansas State for the tournament title Tuesday night.
Tre Demps led the Wildcats (3-1) with 21 points, including 10 straight for his team during a second-half charge that trimmed North Carolina's lead to 48-46 with 17:20 left.
But unlike their game against the Panthers, when the Tar Heels allowed a 29-8 second-half run to put them on the ropes, Jackson and Pinson made sure to answer the Northwestern salvo.
Jackson started it off with a basket at the other end, and Pinson knocked down a 3, before Jackson made two foul shots. Nate Britt hit his own 3 moments later, and a basket by Berry capped a 12-2 run that forced Northwestern coach Chris Collins to call timeout.
The Tar Heels stretched their lead to 20 later in the second half before Northwestern made a brief run in the closing minutes, making the final score look a bit more respectable.
Alex Olah contributed 10 points for the Wildcats, while leading scorer Bryant McIntosh -- who had a career-best 32 against Columbia -- managed 14 points on just 3-for-15 shooting.
The Tar Heels once again played without Marcus Paige, who broke a bone in his right hand on Nov. 3. The senior All-American has been sitting on the North Carolina bench, but the school has yet to indicate when he may be cleared to return to action.
Not that they needed his steady hand Monday night. The Tar Heels only had nine turnovers, a big reason why they were able to answer every Northwestern run.
Northwestern: The Wildcats have won once in five tries against North Carolina. This was the first meeting between the schools since Nov. 29, 1978. ... McIntosh added eight assists. ... The Wildcats were outrebounded 39-26 by the bigger, longer Tar Heels.
North Carolina: Charles Scott, the first black scholarship athlete to play for the Tar Heels, was inducted into the College Basketball Hall of Fame over the weekend. ... Jackson was coming off a career-high 25 points against Northern Iowa. He also had four assists Monday night.