The side looked to bounce back from their 2-0 defeat to Switzerland a few days before, and they did so with Ross Tierney grabbing a later winner.
Alex started on the bench and entered the field in the 72nd minute to help the team to victory in the Spanish sun.
The opening goal of the game came courtesy of a Jay-Ruch Bahuelou own goal before Ramy Najjarine levelled things for Australia with a left footed shot which preceded the late Tierney winner.
The side will play their last match in Marbella when they take on Denmark Under-20s on 5 June at the Dama de Noche Football Centre.
Elsewhere, Denmark took on Germany last night in a friendly fixture with the match ending 1-1. The Danes fell behind after Florian Neuhas struck shortly after the break, but Yussuf Poulsen earned the team a draw when he found the net on 71 minutes.
Despite being included in the Euro 2020 squad, Christian Nørgaard and Mathias Jensen weren’t involved for their nations as they continue to ready themselves for the European Championships behind the scenes following the Play-Off Final victory last week. Denmark play another warm-up game on Sunday against Bosnia and Herzegovina prior to their opening match of the tournament against Finland.