The England assistant coach was Radford’s long-term No2 at the Airlie Birds during which time they twice won the Challenge Cup.
Last year, he stepped up as interim head coach following Radford’s departure and guided Hull to a Super League semi-final before becoming Chris Chester’s assistant at Belle Vue.
However, once it was confirmed in April that Radford would succeed Daryl Powell as Castleford coach in 2022, it was always likely they would link together once more.
Last, 40, said: “I’m really excited to join Castleford.
“I spoke with Lee during the course of the season.
“He reached out and asked if I would be up for the challenge of being his assistant once again.
“It was a tough decision - I was enjoying my time at Wakefield - but the opportunity to work at a great club like Castleford, with the history it has got, and working alongside Lee again, it was a challenge I was really looking forward to and one I wanted to take up.”
With new signings Jake Mamo, Alex Sutcliffe and Kenny Edwards coming in along with Bureta Faraimo, who he worked with at Hull, and Wakefield loose forward Joe Westerman, Last is looking forward to the prospect.
“It’s something which I feel my personality and my character traits are well suited to,” he said.
“I build up good relationships with players, I’m an anorak of the game – I love the game, watch the NRL, like the history of the former great players.
“I’m a little bit of a student of the game and hopefully, we’ll be able to tap into that depth of experience and knowledge here at Castleford.
“I think the squad that Lee has put together, there are some really exciting players coming in and hopefully we can tweak a few things here and there and be successful together again.”
Radford, who has already appointed Hull academy chief Danny Wilson as one of his assistants, said: “I came through the Academy (at Hull) with Andy, played against him at an amateur level as well as professional.
“But then I also got to work with him on the coaching staff. We have had some fantastic success together.
“I love the way he works, his honesty and how diligent and articulate he is as a coach.
“I think that has been recognised recently with his admission onto the England staff.
“The fact that he’s worked at international level with academy, too, shows how highly respected he is as a coach.
“I’m really pleased to get him on board and hopefully having more success with him at Castleford.”
Meanwhile, Wakefield have announced Francis Cummins as one of their new assistants for 2022.