Sheezel signed a two-year extension after his outstanding debut in round one last season and has now added a further four years to the deal.
The 19-year-old's commitment to the Kangaroos' rebuild under Alastair Clarkson comes after he won the club's best-and-fairest award in his first year.
He also earned the league's Rising Star honour and has been added to North Melbourne's leadership group this season.
"I am very excited and very grateful as well for the club for giving me the opportunity to sign on for that long," Sheezel said.
"I love the club and wouldn't want to go anywhere else.
"Ever since I walked in the door, I've just loved the place - the players, the coaching staff and just the whole environment at the club.
"They've made me and my family feel so welcome."
Sheezel joins co-captain Jy Simpkin and key forward Nick Larkey (both 2029) in committing to North Melbourne long-term.
"We're absolutely rapt to have a player and person of Harry's calibre sign on until at least the end of 2030," Kangaroos head of football talent Brady Rawlings said.
"We've loved what we've seen from him so far, and at 19 he's only scratched the surface of what he's capable of.
"His decision to join the likes of Jy Simpkin and Nick Larkey in committing to the club long-term is a great show of confidence in the future of the club, and we can't wait to see what the next seven years hold with him here."
North Melbourne take on St Kilda at RSEA Park on Sunday in their final pre-season hit-out before opening their new campaign away to Greater Western Sydney in round one.
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