After a difficult campaign brought on by a number of high-profile departures, the Whites moved quickly to sure up their squad for next campaign.
Venezuela defender Amorebieta has signed a four-year deal at Craven Cottage after eight seasons in La Liga with Bilbao, while Ghana international Boateng has joined on a one-year deal with an option for a further season.
Fulham have now signed up three players for next season, having taken up an option to permanently sign Sascha Riether from Cologne after a successful season-long loan spell.
However, Amorebieta's arrival is arguably the most impressive addition so far as the west Londoners beat off reported interest from Arsenal, Everton and Zenit St Petersburg.
The 28-year-old defender made more than 250 appearances for Bilbao and will be a welcome addition to what has at times been a shaky Fulham defence.
"I'm delighted to have signed a four-year deal with Fulham and I'm looking forward to competing in the Barclays Premier League next season," Amorebieta told the club's official website.
"I'm impressed with the talent already at the club and I look forward to meeting the players for pre-season training in July."