Ben Barba in action for St Helens.

A ringing endorsement from the Cowboys leadership group  convinced Paul Green to take a 12-month punt on Ben Barba putting his off-field issues behind him to help rebuild North Queensland in the post-Johnathan Thurston era.

The club confirmed Barba's signing on Tuesday night after securing a release from the final year of his deal with Super League outfit St Helens, the deal sealed with the Cowboys paying an undisclosed transfer fee.

Barba has been in tremendous touch during his stint with the English outfit, which followed a brief period with French rugby powerhouse Toulon following the cocaine ban that saw him exit Cronulla.

The NRL has registered his one-year Cowboys deal with Barba already having served his mandatory 12-game ban for a second positive test under the game's illicit drugs policy, which came during the Sharks 2016 premiership celebrations.

It's understood the Cowboys have not imposed any behaviour-related clauses in Barba's deal, and are confident that the likelihood that this is his last chance in the NRL will keep the 29-year-old on the straight and narrow in Townsville.

"We think that we've had a strong culture for a number of years led by our senior players, led Johnathan, Matt Scott, Gavin Cooper, Michael Morgan, people like that," Cowboys head of football Peter Parr told NRL.com.

"All those guys know Ben, they know him better than Greeny or I do, and they want him. He's had a couple of issues but so have other players when they were younger.

"St Helens can't speak highly enough of what he's done off the field over there.

"Given it's a one-year deal, the ball's well and truly in Ben's court to show to us that he can fit in with our culture and that he'll continue on with the same rules and legacy that those guys are implementing.

"We don't have any reason to think he won't do that, we don't believe it'll be an issue and from a footballing point of view, if he's playing his best footy he can add to our side."

Barba's acquisition for the Cowboys continues a significant roster overhaul after their 13th-place finish, with the club set to go all out for Townsville junior and Sharks sensation Valentine Holmes when he officially becomes a free agent on November 1.

North Queensland are also keeping a close eye on Cameron Munster's contract situation and may yet have the salary cap space to go after both Maroons stars given veteran forwards Scott and Cooper are expected to retire at the end of next season.

Discarded Cowboys custodian Lachlan Coote is set to be announced as Barba's replacement in coming days, with St Helens chairman Eamonn McMannus hinting at "announcing a new signing from the NRL shortly" as he farewelled Barba at the club's presentation night.

St Helens are yet to make any official announcement about Coote, while fellow departee Shaun Fensom is also expected to make a move to the UK. 

Leeds Rhinos are understood to be bidding for the fan favourite's services, having recently installed Fensom's former Raiders coach David Furner on a three-year deal.