Fifita, 26, who has represented both Tonga and Indigenous All Stars has penned a deal with Trinity until the end of the season with an option of another year.
Fifita has featured 19 times for the Sharks since joining them back in 2014 from Elite One Championship side Lezignan Sangliers.
Head coach Chris Chester said: “It is a massive signing for the club. As a player we monitored closely over the last six to eight weeks, we know he will bring some real punch and aggression to the team, which is something we have lacked over recent weeks.
“I am looking forward to working with David over the coming months. I would like to take my time to thank Phil Moss and the Cronulla board for releasing David half way through the season.”