44,742 were in attendance to see Ross Stewart score the only goal of the game - a record attendance for an EFL play-off semi-final.
Despite this being a third-tier tie, they beat the existing record set by Aston Villa and West Brom in the Championship play-offs at Villa Park in 2019.
The two ex-Premier League sides are just a couple of the huge clubs in League One this season, with ginormous fanbases to match.
Despite finishing above the Black Cats in the League One table, Sheffield Wednesday were disappointing and struggled to create, as their star man Barry Bannan was marked out of the game.
But, despite their underwhelming display, former Sunderland and Sheffield Wednesday man Micky Gray believes it's still all to play for in front of another huge crowd at Hillsborough on Monday.
"This game is, without a doubt, still in the balance," Gray told talkSPORT.
"Sheffield Wednesday had chances in the second half but Sunderland were the better team throughout much of the game - they've now got to go to Hillsborough on Monday.
"Darren Moore will know his side needs to put in a better performance and they need to show these fans how good they've been this season."
He added: "It's going to be a massive game on Monday and the travelling fans need to make a noise, otherwise this game could flip.
"Hillsborough will be rocking on Monday."