The deal for Mam, until the end of 2029, has been rubber-stamped just as the Broncos prepare to bounce back from their NRL grand final heartbreak and go one better than they did in 2023.
The 21-year-old, who was already on contract until the end of the upcoming season, was in high demand.
The Dolphins went hard for Mam after the 2023 decider, in which he scored three scintillating tries in a losing side.
AAP has been told the Dolphins weighed in with an offer north of $900,000 per season to try and prize the No.6 from the grasp of their cross-town rivals.
Mam was a star turn for the Broncos as they went close to winning last season's grand final. (James Gourley/AAP PHOTOS)
Mam, who has played 38 NRL games and capped a stellar 2023 by being named Dally M five-eighth of the year, resisted the temptation to switch camps; much to the delight of coach Kevin Walters.
"Ezra is a born-and-bred Bronco and it's great that he is staying where he belongs," Walters said
"He is an exciting player but he also likes to get in there and do the tough stuff and what needs to be done for his team.
"We have only scratched the surface on what Ez can do - we'll keep on working with him to improve his game.
"I can't wait to see what we can achieve together."
Broncos skipper and No.7 Reynolds, 33, is on the cusp of signing a one-year extension until the end of 2025, when it is hoped Mam will be ready to step up as the side's new general.
Mam (right) will continue to learn his trade playing alongside Adam Reynolds (left) for Brisbane. (Jason O'BRIEN/AAP PHOTOS)
"Ezra is a massive signing for the Broncos considering the dynamics of the club, with Reynolds likely to finish at the end of next year," Broncos great Steve Renouf told AAP.
"Ezra showed great maturity in his position last year and the way he dominated the grand final was icing on the cake for him and the club and virtually guaranteed his new contract.
"What has been so good for Ezra is that he has learned his trade under the eye of Reynolds, and he will learn so much more from him over the next two years."
Renouf said learning from coaches who were two of the best halves ever to lace a boot was another reason Mam stayed at the club.
"Kevin Walters has played a massive role, that can't be underestimated," he said.
"Ezra has two of the best mentors in the halves that have played the game in Kevin and (assistant coach) Allan Langer. It really doesn't get any better than that.
"(Walters) lets Ezra play off the cuff as he did in the grand final with the razzle-dazzle tries he scored.
"He did that all season and I know Kevvie loves that style of Broncos footy."
Mam has been earmarked by Queensland coach Billy Slater as a State of Origin star of the future and was part of the Maroons 34-man pre-season camp last weekend.
