It is the second time this week the West Yorkshire rivals have done business after Castleford also took prop Suaia Matagi on a season-long loan.
Former St Helens and Hull FC centre Turner, 31, arrives on a one-year deal for 2021 as new Huddersfield head coach Ian Watson continues his reshaping of the Giants squad since moving from Salford Red Devils.
Castleford coach Daryl Powell was in the market for another three-quarter and explained: “Once we realised that Cheyse Blair was definitely going to be a back-rower for us, we were short in the centre.
“I think this is an important signing to stiffen us up competition-wise.
“If you look across our squad we will have strength and depth in every position which is something which I think potentially we didn’t have last year at half-back and centre.
“Those were areas where we got caught out a bit so Jordan will be an important signing.”
Jamaica international Turner, who had a short spell with Canberra Raiders before joining Huddersfield in 2017, can also play stand-off and loose forward.
A former England Knights representative who has made more than 300 career appearances, he said: “I didn’t have to think too much about making the decision after speaking to Daryl and I’m really happy to be here. I’m excited about the coming season, the squad that we have got, and I think we can really push on at the higher end of the table at the end of next year.
“There’s some really good players here in the backline at Cas and I want to come in and add to that.
“There are some players that have been around for quite a few years and although I’ve been about a bit and played a lot of games I am still looking to learn from other people.
“I’m looking to learn off Daryl, looking to learn off people like Michael Shenton and I’m coming here to compete.”
Turner faces competition from captain and ex-England international Shenton - who he replaced when joining Saints in 2013 - as well as Samoa’s Peter Mata’utia with former Melbourne Storm centre Blair now officially switched to the pack.
Oldham-born Turner, who started out at Salford, was a regular in the Giants side this season but - with youngster Jake Wardle in such good form - eventually lost his centre spot once Leroy Cudjoe made his long-awaited return to fitness.
Thereafter, he stood in effectively at stand-off while Lee Gaskell was injured and even played second-row but - with a year left on his Giants contract - has been deemed surplus to requirements by Watson.
But, wherever he has played, Turner has always offered value, not least when memorably filling in at stand-off to help Saints win the 2014 Grand Final.
He is excited by Castleford’s bid to start a challenge for such honours themselves after such a disrupted 2020 campaign for the Wheldon Road club.
“One of the things that really excited me was the spine of the team such as the major coup of Niall Evalds who was pretty sought after,” said Turner, referring to the dynamic Knights full-back who has been secured from Salford.
“I think Niall probably could have had his choice of clubs and he chose to come to Cas.
“Then, with Jake Trueman, Danny Richardson and Paul McShane, the spine is so strong.
“I think it’s one of the main things for going on and doing something well; when you’ve got a strong spine then everyone else going on around it sort of gets on board to be as good as they can be.”