The Australian-born Samoa international joins Brian McDermott’s squad ahead of the 2022 campaign, as Rovers look to make it third time lucky in their quest for promotion.
Featherstone have reached the Million Pound Game in each of the last two full Championship seasons but were beaten on both occasions.
Leilua, 29, has made over 200 appearances in the NRL but was not offered a new deal by Wests Tigers after his contract expired at the end of the season.
“This signing is another clear demonstration of this club’s unwavering ambition and focus on gaining Super League promotion," said McDermott.
"Joey brings a level of experience and raw ability that is unrivalled in the Championship. He’ll add some serious size, strength and focused aggression which will help this side go up to another level.
"I’ve had many conversations with Joey over the last few weeks, we’re looking forward to working together to achieve our Super League objective.”
Leilua will join fellow Samoa international Jesse Sene-Lefao at Featherstone after the former Castleford Tigers man signed for the club last week.
Sene-Lefao is excited for Leilua's arrival, adding: “He’ll bring something that we’ve not had before, he’s like a big front rower out wide.
"He brings that skill and flair alongside size and strength that I think will be great for us next year."
Chairman Mark Campbell commented: “I’m really pleased that Joey has signed, he’s a fantastic acquisition for Featherstone, this is one of the most significant signings in our history, for the Championship and for rugby league in this country.
"He’s a player in his prime at 29-years-old who’s been recognised as one of the best in the game with his Dally M awards, his 225 NRL appearances underline that fact.
"It’s been quite frustrating to see some of the recent comments from fans about new signings, I can tell you now that this is the level at which this club is now operating and there’ll be plenty more to come.
"We need fans to get behind the club now, to invest in us by becoming Blue Wall members, that’s how we continue to go from strength to strength.”
Before joining the club, Leilua will be taking on former England international and NRL star Chris Heighington in a boxing match on Friday December 10.
Rovers intend to show the event at their Post Office Road stadium for fans to come and watch.