Henrik Dalsgaard completed the full 90 minutes as Denmark made it four points from a possible six in Group C.
It was the Danes who landed the first blow on six minutes; star man Christian Eriksen sending a sweetly-struck half volley past Mat Ryan and into the net.
Having missed a golden opportunity to double their lead, the Danes were pegged back seven minutes before the half-time interval. With the assistance of VAR, Yussuf Poulsen was deemed to have handled the ball in the area and Mile Jedinak stepped up to convert his second penalty in as many World Cup games. It was the first goal that Denmark had conceded in six full international fixtures.
Two British-based Australians - Aaron Mooy and Tom Rogic – went close in the second half, while Pione Sisto shot just wide for Denmark. With the final whistle approaching Australia had two chances in quick succession but Kasper Schmeichel saved from both Daniel Arzani and Mathew Leckie.
It’s France up next for the Danes while Australia face Peru.