First journeyman playmaker arrived at Red Hill mid-season, and has recently returned from injury to become a permanent fixture in Kevin Walters' best 17. He was originally brought into the first grade squad having impressed with the Souths Logan Magpies in the Queensland Cup.
Kelly, who has spent plenty of time in the English Super League throughout his career, has been rumoured to be re-signing with the Broncos for the last fortnight.
While the Broncos have struggled badly for much of the season, Kelly's return has seen the club win two in his, and have two losses by tight margins, one to the Newcastle Knights by just eight points and to the Sydney Roosters by a single point in Round 22.
He had a try and three tackle busts in Sunday's win over the New Zealand Warriors.
The half hasn't struggled in adapting back to the NRL at all, having previously started his career with the Cronulla Sharks and Gold Coast Titans, before scoring 67 tries in 117 games in the Super League, an incredible record for a half.
The deal will see Kelly remain at Red Hill until at least the end of 2022, while the Broncos retention rates have been staggering, with Kotoni Staggs, Tesi Niu, Keenan Palasia, Jordan Riki, Kobe Hetherington, Jake Turpin, Tyson Gamble, David Mead, Jesse Arthars, Brendan Piakura, TC Robati, Selwyn Cobbo and Xavier Willison all extending their contracts recently.
Kelly will be battling for a spot next season though, with Adam Reynolds arriving at the club, although it could be comfortably assumed at this stage that Kelly is the most likely man to partner the arriving star.
Kelly said he wanted to stick around in Brisbane.
“I can see the success coming at the Broncos so I wanted to stick around. I can see how hard the guys work and how talented they are," Kelly said.
“We’ve got some good players coming in so it’s going to be a bright future. I’m very grateful to the Broncos for giving me a chance. Hopefully I can pay the club back with some success.”