On the penultimate day of the trade period, the Swans offloaded Blakey, draft pick No.52 and their 2028 second-round selection in exchange for a glut of picks.
The Kangaroos shipped picks No.6 and No.47, a 2027 second-round pick, a 2028 first-round selection and a 2028 second-round pick to get the deal done on Tuesday.
Blakey had five years remaining on his Swans deal, but requested a trade following a fracturing of his relationship with the club.
He was one of five Sydney players who served a club-imposed ban through the AFL finals for breaching the Swans' behavioural standards at the Pullman Hotel in East Melbourne.
The players' punishment was separate to an ongoing Victoria Police investigation into an alleged sexual assault at the hotel.
No charges have been laid, and AAP is not suggesting any wrongdoing.
In his first public statement since the scandal erupted, the 26-year-old offered an apology.
"I want to say that I'm sorry for the events that led up to my exit from Sydney," Blakey said in a statement from North Melbourne.
"I know I have to win back the trust of the broader community, football and otherwise.
"Now I have the opportunity to move forward and I want to thank North Melbourne for helping me find a fresh start."
In an at-times cagey press conference, North Melbourne list boss Brady Rawlings said the club had conducted its due diligence and was "very comfortable" with its position.
Rawlings would not detail what assurances, if any, he received from Blakey about his behaviour that August evening.
"What I speak with Nick is between me and him," he told reporters.
"You probably saw though the media release that he's got a level of remorse about his involvement and being out late."
Rawlings said he wasn't in a meeting where Blakey's recruitment was raised with North's AFLW leaders.
"But clearly we've got Nick in through the door ... so clearly our leaders are comfortable (with) everything that's going on," he added.
The dashing half-back met with Geelong, St Kilda and Gold Coast, but had his head turned by North's eight-year offer, worth more than $11 million.
Asked about his message to any club members who may be upset about Blakey's recruitment, Rawlings pointed to other clubs' willingness to trade for him.
"I think our members would have a lot of faith in our leadership at the club," he said.
"(President) Sonja (Hood), (CEO) Jen (Watt) and (football boss) Todd (Viney) have been massive for this club over the last few years and our board has endorsed everything."
Blakey played 173 games for Sydney after arriving at the Swans as an academy product with pick No.10 in the 2018 draft.
He was also eligible to join North Melbourne or Brisbane as a father-son selection through his dad John, who played 224 games for the Kangaroos, including their 1996 and 1999 premierships.
Blakey's acquisition could mark a step forward for North under new coach Jaymie Graham, after previous failed pursuits of stars such as Dustin Martin, Jordan De Goey and Isaac Heeney.
"It's been well documented for many years we've probably struggled to get a player of this calibre through," Rawlings said.
"Hopefully it opens the doors for many more signings in future years."
After Blakey's mega move, the Kangaroos completed a trade to send former No.4 pick Zane Duursma to Melbourne.
The 21-year-old forward was traded to the Demons along with pick No.52 in this year's draft for picks No.33 and No.49.
North will now turn their focus back to bringing in Adelaide defender Nick Murray and a potential move for Josh Goater to Hawthorn.
GWS veteran Lachie Whitfield, meanwhile, has moved to Carlton for picks No.25 and No.26, along with a 2028 third-round pick.
As well as Whitfield, the Blues received picks 31 and 50.
Collingwood also secured ruck cover after trading a 2028 third-round pick for youngster Flynn Riley.
As the Wednesday night trade deadline approaches, deals are yet to be orchestrated for Keidean Coleman, Jayden Short, Jack Viney and Trent Rivers.
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