The 25-year-old is currently playing for Championship club York but will join the Tigers on a 12-month deal at the end of the season.
Tansey, who can play full-back, centre, wing and stand-off, looked set for a bright future in the game when he burst on to the scene with Leeds in 2006 and had a spell in Australia with Sydney Roosters in 2009. But he was sacked by Hull at the start of last season for a breach of club discipline and moved on to York when Crusaders pulled out of Super League.
Castleford coach Ian Millward said: "We've signed him next year on his outstanding utility value. He has an impressive CV.
"He lost consistency in his life away from the game and went back to York to do the hard yards and get back on track. We're very impressed by his enthusiasm and drive to fulfil his potential.
"We appreciate and respect the guidance he has had from the RFL with various life courses and support. They've given high recommendations that he's ready to re-launch his career and we are providing Jordan an opportunity.
"At the age of 25 he has the talent to be a great utility asset to us."