The 27-year-old was out of contract at the Giants at the end of the season and, after initially joining the Tigers on loan in April on a deal to the end of the campaign, is delighted to extend his stay.
“I’m over the moon,” Patrick said. “It’s a great club to be at. I’ve enjoyed the last five or six weeks and I’m really looking forward to the next three years here.”
Patrick, who played for Wales in the 2013 World Cup, made his Huddersfield debut in 2009 against Castleford and went on to make over 100 appearances for the Giants. He spent the whole of the 2015 season on loan at Wigan.
Castleford coach Daryl Powell said: “We are delighted to confirm Larne will be with us for the next three years.
“He is an experienced front rower whose line speed in defence and ability to break the defensive line is outstanding. He has fitted in well while on loan and we feel he still has a lot of improvement in him.”
Patrick will return to the Tigers team for his fifth appearance against Widnes at the Jungle on Thursday night after being prevented from playing against his parent club Huddersfield last Friday.