Paulo will lead the Samoa squad, which contains five players who played in the NRL grand final, alongside Jarome Luai.
Paulo, 32, comes off contract on November 1 and has yet to secure his future beyond then after a deal to join the Perth Bears fell through.
Parramatta have made it clear they want him to remain at the club.
But there was some conjecture over whether the Eels were happy to let the 20-Test front-rower turn out for Samoa given his struggles with a knee injury in 2026.
However, Samoa coach Ben Gardiner, who unveiled a stacked side that includes Stephen Crichton and Brian To'o ahead of their October 16 pool stage opener against France, claimed Parramatta had given Paulo the green light.
(The Eels) were completely supportive. Junior was really keen to play. There hasn't been any mention of the knee," Gardiner said.
"He's ready to go, he's been training and I spoke to him a couple of weeks ago in Samoa.
"We talked about how exciting it is and how excited he is about the tournament.
"Junior is our most capped player. He's a super proud Samoan, and the opportunity for him to play for his nation again is a very important one for him."
Gardiner has secured a win for Samoa with Dolphins fullback Hamiso Tabuai-Fidow pledging his allegiance to the Toa, despite the lure of an Australian Test jersey which carries a $40,000 payday.
"They want to be able to connect to their roots, and I think that that's something that makes our camp different to other camps," Gardiner said.
Gardiner is deprived of Terrell May and Payne Haas in the front row, with the latter undergoing hand surgery ahead of his move to South Sydney.
The only way Haas could play in the tournament is if a Samoa player has to withdraw through injury.
May withdrew himself to focus on Wests Tigers' pre-season but Samoa's pack remains loaded with forwards that bring power and skill.
Spencer Leniu is included after his grand final heroics for the Roosters, alongside Knights duo Francis Manuleleua and Jermaine McEwen.
"Game changer, phenomenal, I thought his performance in the grand final was an indication of the level of player that he is," Gardiner said of Leniu.
Roosters hooker Benaiah Ioelu is likely to share hooking duties with Jazz Tevaga, who won the Super League grand final with Wakefield last week.
Gardiner's side face France and Tonga in Parramatta either side of a clash with Papua New Guinea in Port Moresby.
Samoa squad: Shawn Blore, Stephen Crichton, Sua Fa'alogo, Clayton Faulalo, Chanel Harris-Tavita, Benaiah Ioelu, Connelly Lemuelu, Spencer Leniu, Jarome Luai, Francis Manuleleua, Deine Mariner, Ata Mariota, Greg Marzhew, Jermaine McEwen, Francis Molo, Junior Paulo, Pasami Saulo, Hamiso Tabuai-Fidow, Izack Tago, Jazz Tevaga, Brian To'o, Enari Tuala, Ronald Volkman.
