"James is an outstanding young talent who we see as a big signing for the Raiders and we look forward to him joining the club at the beginning of the 2015 season," Furner said in a statement on Tuesday.
"The Raiders have followed James's progress from his days at St Gregory's College Campbelltown and we know being from Camden, James will fit into the lifestyle and culture here in Canberra.
"We wish him a successful season for the remainder of 2014 with the Wests Tigers and look forward to him joining us for pre-season 2015."
Tedesco is set to return from an ankle injury for the Tigers' round 13 match against Newcastle on June 8, with the joint-venture enjoying a bye this weekend.
Wests Tigers CEO Grant Mayer said his club couldn't match what the Raiders were offering.
"The discussions with James' management were complex. When another club identifies one of our players as their marquee signing we simply cannot compete with that," Mayer said.
"We wish James well in his new venture and thank him for his dedication and commitment to Wests Tigers over the past eight years."
- AAP