The 23-year-old utility back, who was born in Exeter but raised in Australia, risked all by joining the Rhinos on a three-month trial in November but earned a contract after producing a two-try display in their Boxing Day win over Wakefield.
"He came over for very little money on a trial basis and, if it hadn't have panned out with us, who knows what he would have done," said coach Brian McDermott.
"He didn't have anything else lined up. I already admired him for that, not that that swayed my decision at all. It does give you an indication of what the bloke is willing to sacrifice.
"We had to base a decision on training and playing and he showed up really well.
"I'm pleased it's worked out for him. It's proved you don't have to come through the academy ranks to make it as a Super League player.
"There are 22 and 23-year-old blokes out there playing in the second tier or playing amateur, that can still do it.
"While he's never played an NRL game, he's got enough rugby league experience, he's not a rookie."
Vickery, who has played for Gold Coast Titans' feeder club Tweed Head, almost joined Hull last season but is now set to face them in the champions' opening match at Headingley on Friday week.
He can play centre or full-back but is set to take the wing spot of Ben Jones-Bishop, who has been ruled out for several months after discovering a blood clot in one of his lungs.