Exeter-born Vickery, 23, had his first training session with the Rhinos this week after joining them from Gold Coast Titans' feeder club Tweed Heads, where he scored 17 tries last season.
"My manager told me about the interest from Leeds and I was so excited about the chance to join the best team in the competition," Vickery said.
"Hull FC offered me a deal during last season but things didn't work out in the end.
"However, it is great that I can now come over here and show what I can do. It is an opportunity I want to make the most of."
Leeds, who are still in the hunt for a new centre after failing in bids for Joel Moon and Keith Lulia, are likely to give Vickery his first chance in the Boxing Day friendly with Wakefield.
Vickery added: "I was born in Exeter and moved to Australia when I was four so it is great that my sport has brought me back to England.
"I played football growing up and spent three weeks on trial at Liverpool when I was 15 along with six other players from Australia so it is not the first time that I have been back. I started playing rugby league after that at school and haven't looked back since then."
Leeds chief executive Gary Hetherington said: "Joe has experience of training with the Gold Coast Titans and has been playing regularly in a good side in the Queensland Cup.
"He is English and has good speed and strength. He will feature in all our pre-season games and we will make a decision on whether he remains for the rest of the season before the new campaign kicks off."