The new contract will see him remain at Glasgow Warriors until at least May 2019, subject to visa.
The 23-year-old joined the Warriors from New Zealand Mitre Cup side Waikato last October on a short-term deal until the end of the season.
He has gone on to make 15 appearances for the club and was named the PRO12 Man of the Match in the 47-17 win over the Dragons last month.
The New Zealand-born second-row is a product of Wesley College in Auckland and made two appearances for Dave Rennie's Chiefs in Super Rugby last season.
Speaking to glasgowwarriors.org, Brian said: "I've really enjoyed my time in Glasgow. I've extended my contract for two years and I'm excited for what lies ahead.
"There is a lot of competition within the squad and I've learnt a lot from the other second-rows at the club.
"I have to pinch myself when the supporters chant my name, I've never had that before and that gets me going and keeps me playing hard for the team and the fans.
"It'll be good to work with Dave Rennie again next season, but at the moment I'm just focusing on Gregor (Townsend) and Dan (McFarland) and doing what they want me to do."
Glasgow head coach Gregor Townsend added: "Brian has fitted in really well since joining us earlier this season.
"He has made a number of improvements both physically and in his set-piece play, and he played well during the 6 Nations window.
"We believe that there is a lot more to come from him and we're delighted that he'll continue his development at Scotstoun over the next two years."