The 23-year-old becomes the second player this week to earn a Betfred Super League deal on the back of an impressive showing at the World Cup following Fiji prop Ben Nakubuwai's move to Salford Red Devils.
Ottio was an ever-present as PNG won their group before losing to England in the quarter-finals.
Although Ottio featured at centre in the World Cup, he was a prolific try-scorer on the wing for New South Wales Cup team Mount Pritchard Mounties and could fill the void created by the departure of Corey Thompson.
WATCH: See our new man in action, PNG's #RLWC2017 star, Kato Ottio: https://t.co/MvB8ERoV66
— Widnes Vikings (@WidnesRL) December 1, 2017
The "try-scoring freak", “possessing a lethal combination of size and speed", will be ripping it up for the Vikings in 2018. âš«ï¸âšªï¸ pic.twitter.com/7bFteyykIs
"Kato is a fantastic signing who we are delighted to welcome to Widnes Vikings," said head coach Denis Betts.
"He is a big outside back with World Cup experience. I am excited by the quality that he will add to our edges.
"He is relishing his opportunity to play in the Super League and is looking to make a big impression at Widnes Vikings.
"Kato is a player whose qualities we have seen during the World Cup. I have also spoken to several people in the NRL and connected to Canberra Raiders during my time at the tournament who rate him very highly.
"It is exciting for us to follow the recent signing of Krisnan Inu with another talented outside back who will add competition and quality to the team."
