Wagga City ended a 44-year-old drought after surviving a late scare from Waratahs to claim the Southern Inland title.
The Boiled Lollies were undefeated throughout the regular season and looked on their way to their first top tier title since 1976 before ill discipline struck.
Wagga City scored the first two tries of the second half at Conolly Rugby Complex on Saturday to lead by 18 points, but after having two players yellow carded in the last 20 minutes Waratahs got back into the contest.
Nathanael Mooney set up a thrilling finish when he scored to put Waratahs within six points with 12 minutes to play.
While Wagga City coach Ben Schreiber returned to the field, hooker Darryl Hemopo was then given his marching orders with eight minutes remaining.
However Waratahs couldn't convert and instead it was James Olds who crossed following a break from Schreiber to ensure there would be no dramatic comeback.
Schreiber was thrilled to deliver his new club their long awaited premiership with the 40-29 victory.
"We haven't won one since 1976 and the old boys are really getting around it so it isn't just for the team but for the entire club," Schreiber said.
He was also relieved his yellow card didn't cost them the ultimate prize.
"A stupid mistake by myself nearly cost us the game but the boys really stepped up and were able to come away with it in the end," Schreiber said.
"It goes to show the family culture we've got here.
"Everyone is willing to dig in and work for each other no matter what is going on on the field."
Waratahs had most of the ball but struggled for impact in the first half while Wagga City capitalised on their first chance as Hemopo scored from close range after eight minutes.
Waratahs hit back as James Grimmett charged through to score under the posts and then went in front with a Jayden Stanton penalty goal.
However it was Wagga City who would take a 14-10 lead into the break when Peter Little stepped past Stanton to score two minutes from the break.
Tries to Drew Martin and Noa Rabici saw Wagga City out to a 28-10 and it looked like they could have ran away with things before Schreiber's yellow card.
Grimmett crossed for his second just as Waratahs went up a man before Mooney crossed with Schreiber still on the sidelines.
However the two-time defending premiers didn't take their opportunity late as Olds and Little scored to seal the premiership before Waratahs got one back when Harry Morrow crossed on the last play of the game.
Wagga City captain Nathan Seymour was thrilled to be a part of their drought-breaking title after just falling short against Waratahs in 2016.
"It was unreal," Seymour said.
"It was a bit worrying towards the end when they started to come back, but we knew there was always going to be a second push.
"Tahs are a good team, and have been for the last four years, so it was good to get the win.
"It means a lot to these boys and half the crowd here are old boys so it is good to give them the win they deserve."