Seib will join Head coach Dan McKellar and Assistant coach Laurie Fisher, with a focus on the Brumbies backs and attack.
Seib was at the helm for Queensland Country in their last two National Rugby Championship campaigns and makes the move to the Brumbies having most recently served as Queensland Reds Academy Head Coach.
A long-time coach in Queensland Premier rugby, the 45-year-old guided Brothers to a Minor Premiership in 2019 before taking up his role with the Reds having previously spent five seasons as head coach at Sunnybank.
Plus500 Brumbies Assistant Coach Rod Seib said: “I’m really excited to join the Brumbies.”
“The opportunity to join a world-class coaching staff, and to work with a young group that has already tasted some success in 2020, is an honour for me and a big step in my coaching career.
“The Brumbies have always had an identity of playing entertaining, winning rugby and I’ll certainly work hard to do my part in maintaining that tradition.
“I’ve heard great things about the Canberra community and I truly can’t wait to get started.”
Seib played three times for the Reds, was Queensland club Player of the Year in 1999 and was capped internationally for Australia 7s before enjoying a seven-year stint playing semi-professionally in Scotland.