The 22-year-old signed a contract with the Dragons' NRL squad ahead of the current campaign after coming through the club's youth system.
Antrobus, who qualifies for Wales, links up with a team third in the Championship.
Head coach James Ford said: “He is a versatile, athletic young player who has played at a good level in Australia.
“Bailey comes well recommended by people we hold in high regard in Australia and having looked at a fair number of his games, I think he has a lot of promise and I’m looking forward to working with him.
“He fits into our strategy in that he’s young, hungry, up and coming and keen to fulfil his ambitions.
"We’re really excited to get to know him, build that relationship and help him to do so."