With the scores locked at 8-8 at The Willows, the Tigers scrum-half forced his way over from close range seven minutes from time and Rangi Chase made victory certain with a drop-goal.
Jordan Thompson also touched down and Kirk Dixon kicked three crucial goals for the Tigers while the Reds’ points came through tries from Jodie Broughton and Daniel Holdsworth.
Salford, buoyed by a shock win over Warrington, looked forceful early on. Broughton and Chris Nero both went close but were repelled and Holdsworth was held up over the line.
In the 33rd minute Lee Jewittand Mark Henry created a break and Luke Patten put Broughton over in the corner. Castleford responded, Orr finding a gap in the Salford line.
Orr lost possession but was awarded a penalty and Dixon took the opportunity to kick for goal and halve the deficit to 4-2.
The visitors started the second half much more positively and went ahead as Chase and Richie Mathers created an opening for Thompson on the left. Dixon converted.
Smith stretched the Tigers’ defence as he broke from deep inside his own half but opted not to pass to Broughton and was caught.
Salford quickly shifted the ball out right but Castleford retreated and Sean Gleeson was unable to break through. Gleeson found himself in the right place soon after as a mix-up allowed the ball to bounce and the Reds centre flicked the ball up for Holdsworth to score. Holdsworth’s failure to convert for a second time left the scores tied.
Steve Snitch grabbed a loose ball to give Castleford the chance to attack but Chase, after a brilliant dummy, and Nathan Massey were stopped close to the line. The breakthrough came seven minutes from time after a 40-20 kick by Chase. The Tigers applied the pressure and Orr plunged over from dummy half at close range between the posts.
Dixon added the extras and Chase added the insurance of a drop-goal as time ran out.
Salford Reds: Patten, Broughton, Ratchford, Gleeson, Henry, Smith, Holdsworth, Cashmere, Godwin, Boyle, L. Adamson, Nero, Anderson. Substitutes: Jewitt, Paleaaesina, Sidlow, Neal.
Castleford Tigers: Mathers, Dixon, Thompson, Arundel, Youngquest, Chase, Orr, Jackson, Hudson, Emmitt, Snitch, Ferres, McGoldrick. Substitutes: Fozzard, Massey, Widders, Clark.
Referee: P Bentham (Warrington).