The Ghana international sealed a move to the Cottagers back in May after playing two years for Ukrainian side Dnipro Dnipropetrovsk.
Boateng told the club's official website: "Every footballer's dream is to play in the Barclays Premier League.
"There's some big players in the league. I've been in Spain and it's a good league, but I always wanted to come to the Premier League because of the language, the game and the type of player I am, so I'm so happy to come to a good family club like Fulham.
"It's a big relief for me to finally be here. Fulham were interested a few years ago and this is the third time they've come in for me. They showed me a lot of love and showed so much confidence in me."
Boateng has made 46 appearances for Ghana since making his debut in 2001, scoring one goal.