The 45-test halfback played a key role in the Pumas' run to the World Cup semi-finals but will face off against many of his compatriots when Argentina enters the majority of its first team in the expanded southern hemisphere provincial competition next year.
He offers a timely replacement for Wallabies scrumhalf Nic White, who has left Canberra to play in France.
“We’ve seen through his performances in the Rugby Championship and the great form he showed at the Rugby World Cup, particularly against the All Blacks, Tomas has the necessary skills and knowledge of the game to successfully fit into our structure, and be a game-breaker in Super Rugby,” Brumbies coach Stephen Larkham said in a statement.
The Argentine Rugby Union (UAR) said Cubelli's move was a motive of pride for Argentina since he is a product of the country's PLADAR high performance programme.
"Thinking of the Pumas, it's highly positive that we can have our two top scrumhalves playing in the same tournament as first choices in their teams," UAR president Carlos Araujo said in a statement.
Cubelli has been sharing the Pumas scrumhalf duties since 2013 in the Rugby Championship and the World Cup with Martin Landajo, who will play for the new Argentine Super Rugby franchise.
Semi-finalists in Super Rugby this year, the twice champion Brumbies open their 2016 season against the Wellington Hurricanes in Canberra on Feb. 26.
(Reporting by Ian Ransom/Rex Gowar; Editing by Ed Osmond)
