The Socceroos copped two late goals to suffer a 3-2 defeat to Romania in their friendly match in Malaga, Spain on Thursday.
Australia looked headed for a come-from-behind win after defender Robert Cornthwaite put them ahead in the 54th minute with his third goal in six internationals.
But strikes to Bogdan Stancu and Gabriel Torje inside the last ten minutes ensured the higher-ranked side triumphed.
The mixed performance will give Australia coach Holger Osieck plenty to ponder ahead of next month's World Cup qualifier against Oman in Sydney.
The German coach fielded a strong side, with Cornthwaite partnering captain Lucas Neill at the heart of defence with James Holland another notable selection in centre midfield.
Romania coach Victor Piturca restored most of his key players after they were rested in Saturday's 4-1 friendly loss to Poland.
The Socceroos, ranked 36th and three places lower than Romania, looked disjointed early and were put under heavy pressure.
Stancu had the first decent chance when he fired just wide after Mark Bresciano had coughed up possession while Torje wasted a great early opportunity.
Australia's first genuine chance fell to Matt McKay in the 24th minute but he failed to get a shot on target after some dazzling build up from Robbie Kruse.
The Socceroos looked to be getting on level terms when they fell behind in the 36th minute.
Wilkshire lost possession in a dangerous position, with Mark Schwarzer failing to keep hold of Torje's shot and Christian Tanase firing in from the rebound.
Kruse had a chance to hit back almost immediately when he broke on goal but he scooped his shot over the bar.
But Australia pulled level on the stroke of halftime through a Luke Wilkshire penalty.
Holland played Alex Brosque into space in the box and the striker was clattered by Razvan Dinca Rat inside the box.
Adam Federici replaced Schwarzer just after halftime while Osieck also injected Ryan McGowan off the bench in place of Wilkshire.
Australia took the lead in the 54th minute when Cornthwaite struck.
Neill headed McKay's corner back into the box and Cornthwaite showed good determination to poke the ball home on his second attempt.
Brett Holman squandered a good chance to extend Australia's lead in the 65th minute and Federici denied Stancu with a great save in the 73rd minute.
But Stancu made amends when he levelled the scores in the 80th minute, tapping in following some good lead-up work from substitute Alexandru Maxim.
Romania kept their foot on the pedal and netted the winner just three minutes later, with Federici flat footed as Torje sent in a brilliant free kick after substitute Rhys Williams had fouled just outside the box.
Nikita Rukavytsya, Matthew Leckie and Mark Milligan also saw time off the bench in the second.