The 28-year-old moves to the Madejski Stadium for an undisclosed fee having scored nine goals in 50 appearances during his solitary season at Craven Cottage.
Aluko has now put pen to paper on a contract which will keep him at Reading, where he will wear the number 14 shirt, until 2021.
"In Sone, we welcome a quality player into our squad. With his pace and ability on the ball, he can make life difficult for every opponent we face this season and he has experience of playing at the level we want to play at," manager Jaap Stam told the club's official website.
"He poses a threat going forward, he keeps the ball well, he can play as a striker or out on the wing and I am sure he will improve us as a squad. So I'm very happy that he has chosen to join us."
Aluko could make his debut for the Royals when they host Bristol City after the international break.