The Roar were claiming a record, undisclosed fee for U20 Asian Cup winner Herrington on Thursday.
The 18-year-old will remain with Brisbane until joining the Rapids in January.
The deal comes a day after Adelaide United striker Archie Goodwin, 20, secured a move to Charlotte.
"I have thoroughly enjoyed my time at the club; to have come through the academy from Under 13s makes it even more special," Brisbane native Herrington, who played 17 games in his debut season last year, said.
"Over the past seven years, I have met some amazing people, from management to coaches to players and of course, the fans."
Goodwin scored an equal competition-high 13 goals in 26 appearances for the Reds after joining them from the Newcastle Jets last season.
"Archie is coming off a strong first season with Adelaide United at just 20 years old and we can't wait to see him carry that momentum with us," Charlotte FC general manager Zoran Krneta said.
"His awareness within the box, willingness to run and attack spaces are a few of the top qualities we saw that made us want to pursue him.
"We want to see Archie develop and create good competition within our club."
