The 30-year-old has plied his trade in several leagues across Europe, including spells in Greece, Germany and Spain.
But the Ghana international, who arrives from Ukrainian side Dnipro Dnipropetrovsk, said he is excited by the prospect of playing in England.
"Every footballer's dream is to play in the Barclays Premier League," he told the club's official website.
"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. I called my family and told them 'it's over now'. I can have fun and play my football."
Boateng and Fulham will kick off the new season with a trip to Sunderland next month.