Anderson's three-year deal will facilitate the seamless move of Warriors prop Mitch Barnett to the Broncos next season, also on a three-year contract.
NSW prop Barnett, 31, was granted a compassionate release by the Warriors for next season and agreed to join the Broncos, but Warriors chief executive Cameron George told AAP last month the club was keen to get a fair and satisfactory outcome and secure a player in return.
The delay has been understandable considering the Broncos, like any club, could not force a player to leave when on contract.
Anderson had a deal for next year at Brisbane, but now all parties are satisfied with the outcome the virtual player switch can go ahead.
He has had wretched luck since moving to Brisbane from Melbourne. Anderson made his club debut in the round-three win over his former club and was playing extremely well until he suffered a grade-three MCL injury and fractured tibial plateau in the round-four victory over the Dolphins.
The 26-year-old won't be back in action until at least round 14.
George had said all along that he wanted what was best for the Warriors and for Barnett.
The signing of Anderson was hailed by Warriors coach Andrew Webster.
"Grant gives us depth among our outside backs and will certainly add to competition in the squad," he said.
Broncos recruitment boss Simon Scanlan said Barnett was "a strong leader and a proven performer" at the highest level.
"He brings the kind of professionalism and competitiveness we value highly at the Broncos," he said.
Anderson's move may enhance the chances of off-contract Broncos outside back Jesse Arthars to secure a deal for 2027.
Gold Coast, his former club, did show interest in Arthars when he was not in the side early in the season.
Arthars has since won his spot back and is showcasing his versatility by filling in at fullback for the injured Reece Walsh.
After the win over the Titans in round five, Arthars said he wanted to extend.
"I am off-contract but I do want to stay at this club," he said.
"I have been here for six or seven years now. I have a strong bond with the players in this team and I don't want to go anyway. Hopefully I can get something sorted."
Playing regular NRL will only help the cause of the up-beat Arthars, who did not kick stones when not in the side.
"I am stoked to be back in the team," he said.
"I don't have a negative attitude towards anything. I like to keep everything positive."
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