The 29-year-old Australian, who secured a release from the last year of his contract with Hull on personal grounds, has signed a 12-month deal with the Sharks, where he is expected to provide back-up to regular half-backs Todd Carney and Jeff Robson.
"I'm really happy," Holdsworth said. "It's a great club and it's nice and close to home.
"I watched most of Sharks games this year. They've got a great squad and I'm happy to be in the mix."
Holdsworth, who began training with his new club this week, began his NRL career at St George Illawarra in 2004 and also played for Canterbury Bulldogs before moving to Super League with Salford in 2010.