Wales, who made his Super Rugby debut in 2009, has been called up as a replacement for the injured Brett Sheehan.
Sheehan limped off with an ankle problem in the opening half of Australia's 22-19 victory over Italy in Florence on Saturday.
"A post-game X-ray later cleared Sheehan of any broken bones and he has travelled to Wales with the squad on Monday ahead of the James Bevan Trophy Test, but will be unable to play a part in the match," the Wallabies said in a statement.
"Sheehan will undergo scans in the coming days in Cardiff to determine both the extent of his injury and the course of rehabilitation required."
McKibbin, who spent one season at the Queensland Reds before moving to New South Wales, has made 30 Super Rugby appearances.
"The new player is expected to arrive in Cardiff on Tuesday morning and will become the fourth replacement to have joined the tour following on from Melbourne Rebels trio Scott Higginbotham, Mitch Inman and Caderyn Neville," the Wallabies statement said.
Waratahs lock Kane Douglas has travelled to Cardiff after missing the Italy clash in order to stay near his ill mother in London while he recovered from a knee injury.
Douglas is hopeful of returning against Wales and would be a welcome addition after Rob Simmons was suspended for a lifting tackle during Australia's tour-opening 33-6 loss to France in Paris.
The Wallabies' appeal against the eight-game ban given to Simmons will be heard in Bristol on Tuesday.