Irvine had been without a club since he was released in June last year by English lower-tier outfit Hull City before the resumption of the coronavirus-interrupted 2019-20 season.
"I'm pleased to have everything sorted because as soon as I heard of Hibs' interest, I was keen to make it happen," Irvine said.
"No one has to tell me what a big club this is. I saw it for myself when I was with Celtic and Ross County.
"I had a great chat with the gaffer, who outlined that this is a club that wants to be competing for silverware and qualifying for Europe.
"Why wouldn't you want to be part of that?
"I've missed playing so I'm hoping to be involved as soon as possible.
"I'll work as hard as I can in training and hopefully give the staff something to think about."
Irvine was part of the Ross County team that defeated Hibs to win the 2016 Scottish League Cup and now joins a collective of current and former Socceroos to be on the Easter Road club's books.
"We're delighted to be able to add a player of Jackson's calibre to the squad and I think he'll complement the other players that we have," head coach Jack Ross said.
"Jackson has played at a high level as an international. He can go box-to-box, he offers a goal threat and he's hungry to play.
"He joins us at an exciting time with some big games coming up."