“Besiktas has begun talks with Chelsea for the transfer of Demba Ba,” the club said in a statement, without giving further details.
Turkish media said that negotiations were already advanced and Ba, 29, was on his way to Istanbul for a medical later Wednesday.
Previous reports suggested Beskitas would be acquiring Ba on loan but it was not immediately clear what form the final deal would take.
Under Croatian manager Slaven Bilic, Besiktas will be looking in the coming season to improve on last year’s third place in the Super Lig behind Istanbul rivals Fenerbahce and Galatasaray.
The team also has a place in the qualifying rounds of the Champions League.