Pipping massive international artists including Coldplay, Florence + The Machine, Adele and Ed Sheeran to the post, the lads seemed over the moon.
Rehearsing for their whopper of a Madison Square Garden show in New York, they were unable to hop over the ocean to pick up their trophies, but recorded a nice little message for fans instead.
Just in case any Aussies had forgotten what their own flag looks like, the boys even held one up as a reminder. We'd like to assume it may have also been to cover up the fact that in their excitement, Louis, Liam and Zayn forgot to put on any trousers before they left the house.
Tweeting fans to thank them, Harry said: "Thank you to our fans in Australia and everyone at the ARIA awards for voting us 'Best International Artist' We can't wait to see you!"
Check out what they had to say...
So what do you think? Where were the Aussie accents?