The 33-year-old has joined the La Liga club on a two-year deal and will fill the void left by the recent departure of Kevin-Prince Boateng.
A former Italy international, Aquilani has had permanent spells at Fiorentina, Sporting Lisbon and Pescara after ending an unsuccessful stint at Liverpool in 2012.
“I’m physically fine to play. Prince told me this is an amazing place to play,” Aquilani told the club’s official website. “I really wanted to play in the Spanish league. It’s a new adventure for me after playing in Italy, England and Portugal. I come to UD Las Palmas to contribute with my experience. I consider myself a very sacrificed player.”