The triumph lifted the Wolves up to second in the table – just one point behind next weekend’s Wembley opponents Hull – and nine points above fifth-placed Catalans Dragons with four games left.
Battling Tigers had led 11-10 until Jack Hughes went over in a nail-biting finale to hand the hosts the points.
Castleford recovered from conceding an early converted try to former player Joe Westerman to lead 8-6 at half-time thanks to Denny Solomona’s 32nd Super League try of the season and two Luke Gale goals.
Gale stretched the lead to 10-6 with another penalty before Rhys Evans went over for Warrington, but crucially Kurt Gidley missed the difficult conversion attempt.
A Gale drop-goal edged the home team ahead 11-10, before Hughes took Chris Sandow’s pass to cross for the crucial late score.
Tigers coach Powell, who lost Frankie Mariano with broken ribs, said: “It’s tough to lose like this and I don’t think anyone could have argued if we’d won by a point.
“It was a war of attrition but we nullified Warrington’s strength for most of the game.
“We are going to grow from this and the team has a big future.
“We were not quite smart enough at the end but we are not going to get too down about it.
“Paul McShane was awesome for us and we are showing a different durability and toughness.”
The Tigers were under the cosh from the start and it needed desperate defence to hold up Daryl Clark over the line.
It seemed only a matter of time until the Tigers’ line was breached and the opening score duly arrived in the ninth minute, Westerman ploughing through Larne Patrick’s tackle and touching down. Gidley added the conversion.
Castleford drew level after 26 minutes when smart passing saw Greg Minikin put Solomona over with Gale converting before firing the Tigers ahead for the first time after Chris Hill conceded a penalty.
A Paul McShane 40-20 early in the second half boosted the Tigers, who stretched their advantage to four points with another Gale penalty for offside.
Castleford were dealing competently with everything Warrington threw at them until Sandow’s long pass put Evans over in the corner on the hour.
Sandow missed with a long-range drop-goal attempt six minutes from time and then kicked wide in front of the posts.
Gale then showed how it should be done with his one-pointer, before Hughes touched down for the match-winning try.
Warrington Wolves: Ratchford; Russell, T King, Atkins, Evans; Gidley, Sandow; Hill, Clark, Sims, Currie, Hughes, Westerman. Substitutes: Dwyer, Westwood, G King, Bailey.
Castleford Tigers: Dorn; Hampshire, Crooks, Minikin, Solomona; Chase, Gale; Springer, Milner, Patrick, O Holmes, Savelio, Moors. Substitutes: Mariano, McShane, Cook, Millington.
Referee: C Kendall.