"I'm really excited to be joining this team for the next three seasons and working with my new teammates and new bikes."
Brannigan, 20, earned his first world cup podium in the final round in Norway after bouncing back from serious injury during the season.
"I'm so excited to be a part of Trek World Racing," Brannigan said.
"This feels like the opportunity I need to improve my results and still be consistent. I know any team run by 23 Degrees has produced real talent and I want to make the most of this opportunity to get where I want to be.
"The group of teammates will be great and I'm sure the support will be top notch. I can't wait for this season."
The CEO of 23 Degrees, Martin Whiteley, whose company also manages junior world champion Anton Cooper, said he is delighted to have a strong New Zealand influence in his line-up.
"There's something about the laid-back Kiwi personality that belies their grit and determination to do well half way around the world.
"There is that burning desire and a willing-to-make-sacrifices approach that I've also seen in the likes of Justin Leov and other New Zealand riders."