The 24-year-old scored his third try in four games before teeing up debutant Rory Hutchinson to edge Saints 14-13 ahead at half-time, after Olly Woodburn had crossed to put Exeter in control.
Chiefs retook the lead after the break, with Gareth Steenson passing 2,000 points for the club to make it 19-14.
But Harry Mallinder kicked two late penalties to snatch victory for Saints.
Despite trailing for much of the contest, Northampton were good value for their win - a result that meant they avoided losing three successive home games for the first time in five years.
While France flanker Louis Picamoles caught the eye as a potent ball carrier and hard hitter, it was the brilliance of North that turned the game on its head in the space of three first-half minutes.
With his side trailing 13-0 early on, the former Scarlets back side-stepped his way inside for a trademark finish to reduce the deficit and then superbly set up Hutchinson after a jinking run straight from the restart.
Exeter, losing Premiership finalists in May, remained in touch after the interval and still looked on course for victory thanks to Steenson's accuracy from the tee.
But Mallinder, son of Northampton director of rugby Jim Mallinder, landed a 78th-minute penalty to give Saints their second win of the season.
Northampton Saints forward Courtney Lawes:
"Harry is growing as a player, he is learning from every mistake he makes - unfortunately when you are young you do make a lot of mistakes. He is growing as a character in the team and he is a brilliant player, he did fantastic today with unbelievable composure to get the win at the death.
"We were desperate for that win and I think it really showed out there - we came back twice.
"We really back ourselves, we know we have been playing in patches and if we can string it together for the full 80 minutes there are not many teams who can live with us. We are just looking to stop these lapses of concentration."
Exeter Chiefs head coach Rob Baxter:
"We never really grabbed control in that final quarter. There was an opportunity to squeeze the game out, but crucially we needed to hold up a bit better in the line-out, that is where we lost possession and it started to get a little bit messy.
"We looked a little bit too edgy in that final quarter, we didn't really look like the team going out to win the game and we were on the back foot for too long.
"There was a pretty clear block that opened up some space in their second try, but that is a bit churlish, we missed a couple tackles and sometimes when you get bumped it is because you are not focused."
Northampton Saints: Foden (capt); K Pisi, G Pisi, Hutchinson, North; Mallinder, Groom; Waller, Haywood, Brookes, Lawes, Paterson, Gibson, Clark, Picamoles.
Replacements: Clare, Ma'afu, Hill, Dickinson, Harrison, Kessell, Olver, Tuala.
Exeter Chiefs: Turner; Woodburn, Devoto, Slade, Whitten; Steenson, Chudley; Moon, Yeandle (capt), Holmes, Lees, Parling, Dennis, Horstmann, Waldrom.
Replacements: Cowan-Dickie, Hepburn, Williams, Welch, White, Lewis, Hill, Nowell.
Wales wing George North starred as Northampton came back from 13-0 down to beat Exeter at Franklin's Gardens.