The exchange is initially a loan arrangement, but Tigers say there is “interest from all sides to make this a permanent move sooner rather than later”.
Rankin, 27, played for Gold Coast Titans and Wests Tigers in the NRL and Hull in Super League before joining Giants in 2017.
Wardle, also 27, signed for Tigers ahead of the 2018 campaign after a season with Newcastle Knights in the NRL.
He began his career with Bradford Bulls and spent six seasons at Huddersfield before moving to Australia.
He flew with Tigers to Lanzarote on Thursday for a pre-season training camp, but will return to England this weekend and link up with Giants on Monday.
Rankin can play full-back, stand off or as a winger. He told Tigers TV: “I’m over the moon to be joining Castleford Tigers.
“It’s a great move for me and I’m really looking forward to playing for a club with such a rich history.
“I’ve played against Cas for a few years now and I’m really excited to be joining the playing group here.
“They are consistently in the top four of Super League and they’ve shown numerous times how good they are and the points they can score from anywhere on the field, which is quite admirable for my game.”
Tigers have lost scrum-half Luke Gale to a long-term Achilles injury and Rankin added: “I’d like to see myself playing in the halves here at Castleford, it’s the position that I feel most
“I’m a running half so that is a part of my game that I really want to bring out here at Cas.
“They like to throw the ball about so something I’m really look forward to is playing off the back of this forward pack.
“They have some great outside-backs that finish some incredible tries. I wouldn’t turn down the full-back spot because I’m happy to play in any position for this squad.
“It’s a very intimidating place to come and play is the Jungle, not just because of the way that Cas play but because of the supporters.
“They come out in numbers every week and I’m really looking forward to having the opportunity to come out here in a Cas shirt this time and be welcomed instead of the other way around.
“I can’t thank the club enough for giving me this opportunity and I can’t wait to get stuck in with the boys and meet all of the fans.”
Tigers’ director of rugby Jon Wells said: “Jordan is a player I have admired for a few years now and we’re delighted to welcome him to the Tigers.
“He’s a very experienced, high-quality player who we think will be a great fit at the club. He is a fantastic competitor who can provide options in a number of positions and further strengthens our backline, so we can’t wait for him to get started with us.”
Wells went on: “I would like to place on record our thanks to Huddersfield and [chief executive] Richard Thewlis for working with us on this and in particular Joe Wardle and his manager Iestyn Harris for their professionalism in what has been an uncertain time for Joe.
“We wish Joe all the very best in this next stage of his career.”
Thewlis said: “This move came about very quickly within the last 24 hours and we’ll be delighted to welcome Joe back.
“He will fly back from camp over the weekend and we’ll see him for training on Monday morning
with the squad.
“Simon [Woolford, Giants’ coach] was looking for back-row and centre competition and Joe clearly brings this to us and of course has the chance to play in Super League alongside his brother.”