Katoa debuted for the Sharks earlier this season. So far he has crossed twice in six appearances.

The 20-year-old flyer, who was born in New Zealand, joined Cronulla in 2016 from Parramatta.

"I'm enjoying playing in the Sharks NRL side with so many experienced players and I'm grateful for the opportunity I'm being given," Katoa said.

"I just want to go out, do my job and not let the boys down. Hopefully that's been happening and I can keep doing that. I'm excited about the rest of this year and looking forward to the next two seasons as well."

Sharks coach Shane Flanagan was pleased to keep the winger.

"It's important that we retain the talented young players we have at the club and we are very pleased to have Sione around for at least two more years," Flanagan said.

"He was a part of a very good NYC team last year, was the leading try-scorer in that competition and made the Holden Cup team of the year and while it's only early days he gives every indication that he will develop into a quality first grade player and enjoy a long and successful career."