The winger struck in the 90th minute to settle a rip-roaring encounter which might have gone either way until his intervention.
It was no more than Gus Poyet's men deserved after creating the better chances on an afternoon when they collected just their third Barclays Premier League win of the season.
Black Cats striker Steven Fletcher was denied by the crossbar before the break and Connor Wickham, Jordi Gomez and Johnson all passed up glorious opportunities to open the scoring.
But goalkeeper Costel Pantilimon had to pull off fine second-half saves from Ayoze Perez and Moussa Sissoko as the Magpies threatened to end their run of defeats before Johnson dashed their hopes in front of a passionate crowd of 52,315.
Sunderland were dealt a significant blow before kick-off when full-back Anthony Reveillere limped out of the warm-up with a calf injury.
Poyet replaced the Frenchman with central defender Sebastian Coates and asked skipper John O'Shea to start at left-back, and the visitors looked understandably shaky as their hosts flew out of the blocks.
However, for all their possession and the driving efforts of Sissoko and lively lone striker Perez, they were unable to trouble Pantilimon to any extent until Sissoko exchanged passes with Sammy Ameobi and drilled in a low 14th-minute effort.
But as the initial onslaught abated, Sunderland found their feet at the back to give the men ahead of them a platform to start creating, and it was they who settled into the better rhythm with striker Fletcher giving them an outlet with the commendable assistance of wide man Wickham.
The England Under-21 international perhaps should have scored with a header from Johnson's 23rd-minute free-kick, and Fletcher was unfortunate not to do so three minutes later when he got ahead of defender Steven Taylor to sidefoot Sebastian Larsson's whipped cross against the bar.
Wickham forced a fingertip save from rookie goalkeeper Jak Alnwick on the half-hour after unleashing a fierce drive and after Perez had sent Pantilimon scuttling across his goal with a curling effort, headed straight at the 21-year-old from Santiago Vergini's delivery.
But despite all the endeavour, a half which brought five bookings ended goalless with the Black Cats leaving the field ahead on points.
The visitors resumed in confident fashion with Newcastle still struggling to find a real coherence, and their fortunes could have taken a turn for the worse five minutes into the second half had it not been for Taylor's bravery.
Wickham did superbly to recycle the ball and clip a cross to the far post, where the defender managed to get there marginally before Fletcher before colliding in sickening fashion with the upright and suffering a head wound in the process.
The visitors should have taken the lead while Taylor was being patched up off the pitch when Fletcher handed Gomez the chance to make a name for himself on Wearside, but the midfielder sidefooted wastefully wide.
Pardew replaced Yoan Gouffran with youngster Adam Armstrong with 31 minutes left on the clock, but it was full-back Daryl Janmaat who took aim at the Sunderland goal seconds later, although his left-foot strike flew well wide.
But Perez came desperately close to opening the scoring when he dispatched Sissoko's 63rd-minute pass towards the top corner only to see Pantilimon pull off a superb one-handed save.
Sissoko failed to connect with Ameobi's 67th-minute cross after turning neatly inside his own half and sprinting upfield to play in the wide man, and Armstrong was denied by Pantilimon after Perez and the increasingly influential Sissoko had combined to set him up five minutes later.
Armstrong fired straight at the Romanian goalkeeper once again after creating space for himself 16 minutes from time, and it was then that Pardew chose to send on striker Papiss Cisse for defensive midfielder Cheick Tiote.
The visitors might have gone ahead with 13 minutes remaining when Wickham picked out Johnson and he stepped inside Fabricio Coloccini only to then stab his shot wide.
But the winger made amends with seconds of normal time remaining when, having held off Sissoko and stayed on his feet to spark a pacy counter-attack, he collected substitute Will Buckley's lay-off and thumped the ball past the helpless Alnwick.
Source : PA
Source: PA