Fulham have paid an undisclosed fee to Norwegian club Aalesunds for Finland international Sakari Mattila.
The 26-year-old defensive midfielder has agreed a two-year contract with an option for a further 12 months.
“From day one when I heard about the interest, I was looking forward to this moment,” he said.
Mattila, who has six caps, could make his debut in the club’s opening game of the new Championship season at Cardiff City on Saturday.
He is Fulham’s seventh summer signing following the arrival of fellow midfielders Tom Cairney, Jamie O’Hara and Ben Pringle, defenders Jazz Richards and Luke Garbutt, and goalkeeper Andy Lonergan.