North Korea unleashed 21 shots to four and enjoyed 62 per cent possession, but it was Australia who walked away with the spoils courtesy of mesmerising strikes from Alanna Kennedy and Sam Kerr.
The win set up a semi-final showdown against China at Perth's Optus Stadium on Tuesday night and also also guaranteed the Matildas' qualification for the 2027 World Cup in Brazil.
Australia's Asian Cup title hopes were dealt a blow a week ago when the 3-3 draw with South Korea in Sydney relegated the hosts to second spot in Group A.
Arnold was disappointed with her performance in that match, but she bounced back against North Korea with a series of stunning saves.
The 31-year-old missed the first two games of the tournament with a calf niggle, which came on top of being largely out of action for several months due to it being the off-season for her National Women's Soccer League side Portland Thorns.
Arnold, the penalty shootout hero against France in the 2023 World Cup, says her huge display on Friday night gave her confidence she is back to her old self.
"It was a long time coming for me," she said.
"I probably haven't had the best performances in the international (scene) leading up for this game.
"So yeah, I'm glad I could come in and do my job and sort of feel like myself again after three or four months of no games and limited training."
Arnold believes the grit Australia displayed against North Korea will leave them in good stead for the rest of the tournament.
"I was talking to (Kaitlyn Torpey), and we were saying that every tackle and every clearance and everything that went on, you just wanted to celebrate every single thing," Arnold said.
"And I think that's what really got us over the line at the end of the day, that we all had each other's back. We were all celebrating each other."
Hayley Raso has missed the past two games with concussion and Steph Catley the ;ast one, and it remains to be seen if they are passed fit to take on China, who booked their own spot in the final four with a 2-0 extra-time win over Taiwan on Saturday.
In Catley's absence, Torpey filled in superbly at left-back, and Matildas coach Joe Montemurro has full faith the 25-year-old can do the job again if needed.
Torpey praised Catley for giving her excellent advice on how to tackle North Korea, and she's confident the result will help propel the Matildas to greater heights.
"That game gave us a lot of motivation," Torpey said.
"Straight away, Joe said, 'let's go win this thing now'. So I think that was such a good step forward.
"We can put up a fight and we are ready for anything that comes at us. Everyone's ready to win this."
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