Delaney, 28, had two years remaining on his previous contract but that has now been replaced with a new deal, at the end of which, he will have been at the Rhinos for nine seasons.
The second-row, who is currently sidelined with a knee injury, has made 109 appearances for the club having signed from NRL side Gold Coast in 2010.
Speaking about his new contract Delaney said, “I am very happy at the Rhinos and was happy to see out the remaining two years of my contract here and see where that took me. There was a lot of rubbish coming out of Australia saying that I was looking to move home but that was never my intention.
“It was flattering that club’s were enquiring about me but I have never felt more at home at a club than I do at the Rhinos. When Gary Hetherington offered me a five year contract, the decision was an easy one and it feels good to know that I will be playing out the remainder of my career at this great club.”
Head coach Brian McDermott added, “Brett is a key member of our squad and coming into his best years as a forward over the next five years. His workrate and determination are incredible which is why he has so much respect from his fellow team mates and opponents.
“I think it is a great message for us as a club and Super League as a competition that a player of Brett’s quality has committed himself in the long term to the Rhinos.
“Because this is Brett’s fourth season at the club, people probably underestimate how much rugby is still in him, he came to us when he was just 24 and has become an integral part of our club in those intervening four years and I am delighted he has agreed this new contract.”