Marshall praised Frizell's preparation as "the most professional player I've ever seen when it comes to preparation,'' after Wests Tigers confirmed the 35-year-old's 2027 signing.
Frizell joins from Newcastle, whose side reached this year's NRL Grand Final, and brings 306 games' experience.
He has represented Wales, Australia, Tonga and New South Wales, and is in Tonga's World Cup squad this year.
His return for Tigers pre-season at the new year depends on Tonga's progress at the tournament.
The Tigers seek depth under Marshall after a strong 2026 start gave way to a late-season slump amid club and playing-group issues.
"I'm really looking forward to joining the Wests Tigers in 2027," Frizell said.
Frizell said he was grateful to join the project and hoped to guide young players through his experience and leadership.
Marshall said Frizell would be invaluable to younger players and model first-grade preparation week after week.