Magpies skipper Kevin Nolan looked to have won the game with his audacious 52nd-minute strike, but with the clock having ticked into the fourth minute of injury time, Gyan almost involuntarily nudged the ball over the line after Steve Harper could only parry Phil Bardsley's shot.
Newcastle will be bemoaning the loss of two points which were firmly within their grasp for all but a few seconds of a tense encounter despite the absence of Andy Carroll, Cheik Tiote and Steven Taylor, three of the club's most impressive performers this season.
They dominated the game after Nolan's strike, his 10th of the season - the first time he has reached double figures in the Premier League - and headed off on the short trip back to Tyneside kicking themselves.
In the long run a return of four points from a possible six against their arch-rivals will be more than satisfactory, and a face-saving draw will do little to quell the disappointment for the bulk of a crowd of 47,864.
It was all too much for one home fan who was arrested on the pitch after making his way over to Harper and there were ugly scenes after the final whistle.
Having seen his players under-perform so drastically in the 5-1 drubbing at St James' Park in October, Sunderland boss Steve Bruce sent them out for the return under no illusions as to what was required of them.
Opposite number Alan Pardew was not at Newcastle the day the Magpies secured their biggest derby victory in 55 years, and his players needed no reminding of what lay ahead of them as the locals gathered intent on retribution.
By the time Howard Webb's whistle sounded to mark the end of the opening 45 minutes, it was debatable which of the two managers was more pleased.
Pardew will have been happy enough with the scoreline, which remained at 0-0 despite Harper being busier than counterpart Craig Gordon, although Bruce may have been relieved that the Magpies had been unable to convert a series of good chances which had come their way.
The visitors could have been ahead with just three minutes gone after Joey Barton carved open the home defence.
His floated ball over the top allowed Shola Ameobi to beat the Black Cats' offside trap and bear down on Gordon, but although his shot beat the Scotland international, it ran agonisingly wide of the post.
Sunderland responded and Darren Bent might have opened the scoring three minutes later after being played in by Steed Malbranque.
However, after cutting inside central defender Fabricio Coloccini, who otherwise enjoyed an impressive first half, the England striker saw his shot blocked by Harper's foot.
Newcastle threatened once again with 12 minutes gone when, after Barton's corner had been half-cleared, Coloccini fired towards the bottom corner and Kieran Richardson hacked off the line.
Harper had to get down smartly to keep out Malbranque's 18th-minute drive and Nolan's block accounted for Jordan Henderson's well-struck effort from distance in injury time, although Ameobi had earlier headed over from another Barton corner.
Bent had a glimpse of goal four minutes after the restart when he ran on to Bardsley's long ball, but with Harper advancing to meet him, he lifted his lob over the keeper but wide of the post.
The miss proved costly within three minutes when Ameobi got up above Anton Ferdinand to meet Barton's corner and head down for Nolan to back-heel audaciously past Gordon from point-blank range.
Sunderland were in some disarray as Newcastle dominated possession, although Harper was relived to see Richardson deflected Ahmed Elmohamady's driven 66th-minute cross wide.
The home side worked desperately to force their way back into the game but lacked any real guile or craft.
With Coloccini and central defensive partner Mike Williamson in imperious form against an impotent strike-force of Bent and Gyan, the minutes ticked away with little sign of an equaliser.
But four minutes into injury time Harper failed to hold Bardsley's shot and Gyan bundled the ball home from close range to spare his side's blushes.