The 22-year-old spent the first half of the last season on loan with the South Coast club, but he was recalled by Blues manager Antonio Conte in January.
However, despite impressing for Eddie Howe‘s side, Ake could make only two league appearances for the Blues.
“The decision to come here was to be able to play more games which is important for me and that is why I came here,” Ake, who has joined the Cherries in a £20m deal, said.
“There are no guarantees that I will play coming here but if I train hard and play well then I will have a chance.”
Source: Tribal football