Kersten, who grew up in WA, was one of the Dockers’ primary targets this trade period and requested a trade to the club earlier this month.
“Shane had a strong year in 2016 playing in Geelong’s forward line, where he showed his ability to play his role and kick goals,” Fremantle’s general manager of list management Brad Lloyd said.
“We look forward to Shane adding to Fremantle’s forward line and being a long-term player for the club.”
The 23-year-old played 13 of the opening 14 games of the season, however, struggled to cement his spot in the side in the second half of the season, playing just four games in the Cats’ final 10 games and sought a trade in search of more regular senior football.
He is the Dockers’ fourth acquisition this trade period.