Alexander, 32, has signed a one-year contract extension with the side, keeping him at the club until the end of the 2018 season.
The extension will likely see him become the club’s all-time most capped player in the franchise’s history.
Alexander has made 142 appearances for the Brumbies, scoring 21 tries, while also playing 72 times for the Wallabies.
“I am thrilled to be able to sign for the Brumbies for another year,” Alexander told the club’s website.
“The Brumbies have been a major part of my life and I am looking forward to the challenges that lay ahead.
“I am proud to have represented the club and it’s something I want to continue to do for a while yet. I have enjoyed many special years with the club and have enjoyed playing with some top-quality players whilst here in Canberra.
“Our current group has plenty of potential to achieve great things and I am delighted that I will be able to help the club achieve our goals.
“I see exciting times to come for the club and am positive about the that we are heading. The promotion of Dan McKellar to Head Coach and the return of Laurie Fisher points to a great year ahead.“
The Brumbies’s next fixture is against the Reds on July 7 at Suncorp.