Aboubakar has already arrived in Istanbul to complete a move to Besiktas.
— Portista (@FCPortoGlobal) September 23, 2020
Aboubakar, 28, will leave Porto on a free transfer six years after joining the club from Lorient.
In his time at Porto, the Cameroon international scored 58 goals in 128 appearances.
Besiktas took Aboubakar on loan for the 2016-17 season in which he bagged 19 goals.
He will now return to the club on a permanent deal after Porto reached an agreement to terminate his contract.
Ze Luis to Fenerbahce
Porto are also offloading Cape Verde striker Ze Luis to another Istanbul giant, Fenerbahce.
The 29-year-old will join Fenerbahce on loan with an obligation to buy for €6m, O JOGO reports.
Porto signed Ze Luis from Spartak Moscow just over a year ago, paying a €10.75m fee.
But his 10 goals in 31 appearances failed to convince Porto, who are now letting him go.
English side Tottenham almost signed Ze Luis on loan during the January transfer window.
But his future is in Turkey where he will sign a three-year deal with Fenerbahce.