The ex-Sydney Roosters star joins the East Yorkshire club on a three-year deal.
Equally at home at centre or second-row, the Scotland international is a major recruit for Tim Sheens ahead of 2019.
“Kane is obviously a very experienced NRL player with over 180 first-grade games,” said the Australian coach.
“He’s 29 years-old and plays both centre and second row which will give us a lot of depth in that area.“Kane is a very professional player, a very good player but also a very good person so I think he will add to the culture of the club.”
Linnett, who won the NRL premiership with Cowboys following their famous win over Brisbane Broncos in 2015, has also made five Test appearances for Scotland, and is a powerful ball-carrier.
His capture follows on quickly from the signing of fellow Australian Mitch Garbutt, the prop who arrived from Leeds Rhinos earlier this week.
Linnett has scored an impressive 54 tries in 162 games for Cowboys - including one against Leeds Rhinos in the 2016 World Club Challenge success since joining them from the Roosters.
He said: “I always wanted to finish my career in the Super League.
“I’m really excited to get over there and meet a new bunch of boys, get settled in, work hard and hopefully have a good year.“Having a senior role, I’ve got a lot of experience in the NRL so I’d like to help some of the younger boys through and it would be great to win a Super League title.
“I’ve played a couple of finals here in the NRL, so that would be the ultimate achievement."Linnett will join up with the rest of the Robins squad at the end of November once his visa and paperwork have been granted.