Outplayed at the start, Salford showed both craft and resilience gradually to take control, with two tries in eight minutes midway through the second half wiping out the heartache of Headingley when they believed they were on the way to the final.
Sheffield were by far the sharper side in the early stages and got a quick reward in the shape of a memorable try, fashioned by two of their Wembley heroes. Keith Senior stood in the tackle and slipped the ball to Waisale Sovatabua, then supported the Fijian full-back's weaving run to take his inside pass and complete a spectacular 70-yard move.
Mark Aston did not convert and the Eagles could not turn their dominance into further points, even when the Salford captain, David Hulme, spent 10 minutes in the sin bin for one of the match's constant stream of holding down offences.
Sheffield, steadily coming into the game, gained ground through the power of one new signing, Neil Baynes, and the ball skills of another, Darren Brown, and narrowed the gap during Hulme's absence when Mark Aston was caught offside from a Martin Crompton kick. Steve Blakeley landed the resulting penalty.
With Sheffield's new signing Simon Baldwin in the bin, also for holding down, Salford twice came close to a try before half time; first when Blakeley took Baynes' pass and was stopped on the line, and then when Scott Martin almost got to Bobby Thompson's kick to touch down.
Sheffield had to withstand more pressure at the start of the second half, but Blakeley missed an excellent opportunity to equalise when he skewed a penalty wide. Aston made no such mistake when he was presented with a similar chance, after Gary Broadbent was harshly penalised for dropping on a loose ball.
But then Salford's new Australian second-row pairing took command, Hudson Smith taking the ball 40 yards out to go free for one try and Brown throwing the long pass to Thompson that set up Martin for the second.
Blakeley converted the first, missed the second but then gave Salford a match-winning lead with two penalties as Sheffield lost their discipline; Darren Turner and Dale Laughton ending a gripping tie by watching their side surrender the Cup from the sin bin.
Salford: Broadbent; Martin, Casey, Thompson, Carige; Blakeley, Crompton; Baynes, Alker, Southern, Smith, Brown, Hulme. Substitutes used: Highton, Faimalo.
Sheffield: Sovatabua; Lovell, Powell, Senior, Sadje; Pearson, Aston; Laughton, Lawless, Shaw, Hardy, Turner, Doyle. Substitutes: Molyneux, Stephens, Baldwin, Watson.
Referee: J Connolly (Wigan).