The Northern Irishman was greeted by a rousing reception on Wearside as he took to the dugout, but the half-time whistle was met with a handful of boss as the home side went into the break a goal down after Simon Vukcevic struck on 17 minutes.
However, a late resurgence saw David Vaughan score a screamer to equalise on 84 minutes before Sebastian Larsson scored an excellent free-kick in stoppage time to claim a remarkable win that lifts the Black Cats two points clear of the relegation zone.
Blackburn's perennially-beleaguered manager Steve Kean must have been grateful to have the spotlight taken off him for once, and for so long his team looked like claiming back-to-back league wins for the first time in his year-long tenure.
In the end, his team relented in the face of increasing pressure and possession from the home side, and they remain in the bottom three with only Bolton Wanderers beneath them in the standings.
O'Neill has certainly appeared to have injected a shot of confidence into the Sunderland camp upon his arrival at the club he supported as a boy, but they still look a side as devoid of creativity as they did during Steve Bruce's final days in charge.
The Wearsiders started brightly and enjoyed the majority of the possession, but they could not create any chances much clearer than Phil Bardsley's in only the third minute. Bardsley and Jack Colback got in each other's way on the edge of the box as they both went to latch on to Stephane Sessegnon's pulled back pass, and the defender eventually fired over the bar.
Another characteristic of Bruce's latter-day Sunderland was their poor organisation at set pieces, and that proved their undoing when Blackburn took the lead.
Morten Gamst Pedersen's free-kick from deep on the left was pinged across to Christopher Samba, who was allowed to bring it down with his feet inside the box. The big defender then saw his shot palmed away by Sunderland keeper Keiren Westwood, only for Vukcevic to pounce and head into the unguarded net.
The goal was the first in the Premier League for the Montenegrin midfielder, who was sporting a face mask to protect his broken nose that would not look out of place at a Regency masquerade ball.
Sunderland should have by rights been two goals down at half-time when Westwood came off his line to claim a Pedersen delivery but bumped into the unsuspecting Samba. Scott Dann reacted quickest to head home, but the whistle had already gone for a perceived foul on the Sunderland keeper.
After the break the same theme continued and developed, with Sunderland having as much as 75 per cent of the possession during the second half. Blackburn seemed happy to sit back and defend their lead and Samba was imperious as he repelled everything that came his way.
Kean was forced to make all three of his allotted substitutions before the hour mark as Gael Givet, Michel Salgado and Martin Olsson - himself a first-half replacement for Givet - all had to come off.
O'Neill had the luxury of using all of his changes for tactical reasons, and with 15 minutes remaining he brought on James McLean and Ji Dong-Won. The former made an immediate impact as he sent in several testing crosses, but it took something special for Sunderland to get on the board.
That duly arrived when, with six minutes of normal time remaining, substitute Adam Henley's defensive header only went as far as Vaughan, and it sat up perfectly for the Wales midfielder to hammer home his first goal for the club with an unerring 20-yard strike that Robinson could only watch as it flew past him.
Things got even better for Sunderland when, two minutes into injury time, Mauro Formica handballed on the edge of the box. Larsson stepped up and bent in an excellent free-kick that rebounded off the inside of the near post and behind Robinson.
That free-kick will have been of special significance to Larsson, who had his penalty saved against Wolves last weekend in a match Sunderland went on to lose 2-1.
The thrilling denouement was tempered somewhat by serious injury to Blackburn defender Jason Lowe, who left the field on a stretcher after colliding with Larsson in mid-air, but the final whistle still brought with it a rapturous cheer from the home side for their new manager.
Blackburn, meanwhile, still await their first away win and their first clean sheet of the season, and face another huge relegation six-pointer at home to Bolton two games from now.
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