The winger should now stay at the club until the end of the 2018 season.
“I’m so happy to have extended my deal to stay here at Cas Tigers for the coming three seasons,” said the 22-year-old winger.
“Everyone has made me feel at home here and we have a great team both on and off the pitch.
“I’m surrounded by players and coaches who are helping me to constantly improve my game, and I know I can continue to grow as a player in this environment,
“Nothing comes close to playing here at the Jungle! Our fans are awesome and I can’t wait to get back to business when the new season begins in February.”
Tigers head coach, Daryl Powell is pleased the the player has committed to Cas.
“Denny can become the best winger in Super League if he continues the hard work and application he has shown so far this preseason,” he said.
“He is a natural finisher with speed to burn. I’m looking forward to helping him achieve his huge potential over the next three years.”