The agreement was announced on Friday, just one day before the Dragons face the Parramatta Eels at Pirtek Stadium. St George Illawarra confirmed Marshall, 29, would make his NRL comeback in the match, with coach Steve Price declaring Marshall had looked fit, full of energy and "very confident" at three training sessions during the week.
"He's been fantastic, it's like he hasn't been out of the game to be honest," Price told Dragons TV.
"He's fitted in really well, he's ticked all the boxes which we asked of him and he'll be taking the field come three o'clock tomorrow afternoon."
Watch the NRL LIVE with a 2-week free trial.
Get the NRL Digital Pass now!
"They will certainly complement each other as we go forward in coming weeks," he said.
"It's a healthy position to be in and it just gives us strike on both parts of the field."
Having recently ended a failed attempt to convert to rugby union, the brilliant five-eighth will be back in top-flight rugby league in just over 24 hours.
“The whole process has been complex but all parties are pleased to see that Benji will return to rugby league,” Dragons CEO Peter Doust said.
“We understood and respected the position of the Wests Tigers, we had a similar clause in the contract of Mark Gasnier when he left to play rugby union in France, the only difference being that he returned to our club."
Price added: “The coaching and performance staff are satisfied that Benji is fit to return to the NRL.
“Benji has ticked all the boxes this week and is very keen to get back out on the field and play.
“He has trained well and fitted in really well with the group and we know that he will only get better as the weeks go by and he gets more rugby league training and games under his belt but we are looking forward to having him as a part of our team tomorrow."
Wests Tigers boss Grant Mayer said he was pleased Marshall could make his comeback.
“I’d like to thank Peter for his willingness to work with Wests Tigers to reach an agreement that was acceptable for both clubs,” Mayer said.
“First and foremost Wests Tigers are very happy that Benji is back in the NRL and look forward to seeing him play for the Dragons.
“We have the upmost respect for Benji, he’s a Life Member of Wests Tigers and played 201 games for the club over 11 seasons. Benji will always be a part of this club no matter which team, or code, he plays.
“We have been consistent with our messaging since Benji announced his desire to return to Rugby League, this negotiation was about protecting the sanctity of the contract which Benji had with Wests Tigers for the 2014 and 2015 seasons.
“The agreement we’ve reached with the Dragons is not onerous or over the top, and we believe is a fair commercial set of terms for a marquee player such as Benji to be taking to the field for a rival club.
“Moving forward I believe our game his reached a stage where transfer fees will become the norm, we see it working in other professional sports and given that Rugby League is now a billion dollar business the time has come for it to become common place.”