Their two matchday 23s will be foes on Sunday morning (AEDT), but Australia and Wales's wider squads joined forces ahead of their Cardiff encounter.
The non-playing Wallabies and Welsh trained at Wales's training grounds, the Vale on the outskirts of Cardiff, going head-to-head in a session that would normally be self-contained.
Wallabies defence coach Nathan Grey helped arrange the session, keen for the players to have a slightly different opposition in training.
"We thought it would be a great concept to try and get the guys working together and create that competition," he said.
"They train hard against each other but just to have that little bit of opposition, little bit of extra competitiveness in what we're doing and the quality was really good."
"You're testing that skill under a different type of pressure.
"They obviously train against the players during the week, the starting guys, but to do it against an opposition you don't quite know what they're doing or how they're going to react (is beneficial)," he said.
"Also from a defensive perspective as well, they're throwing different things,different skill sets and different opportunities that you've got to work at.
"That was a real positive and a real bonus of doing the session we did.
Both groups paused for a moment's silence at 11am to acknowledge Remembrance Day, commemorating the fallen soldiers of Commonwealth countries.
The move comes just days after Wales and England joined together for an unprecedented scrummaging session in Bristol.
Australia takes on Wales on Saturday November 11, kicking off at 5:15pm local, Sunday 4:15am AEDT, LIVE on beIN Sports and SBS.