Mandanda's management agency Classico Sport reportedly told that the deal is 90 percent done.
The statement in regards to the deal being 90 percent complete read: "We cannot say the transfer has been completed just yet. Marseille want €1.5 million for him and talks are still ongoing."
Liverpool are also interested in Mandanda as are Aston Villa, Newcastle United and Norwich according to the Daily Star.
Mandanda has 21 caps for the French national team but is out of contract at the end of the season and Marseille are willing to cash in before the summer.
The 31-year-old keeper is vastly experienced and has made 414 appearances for Marseille over the years winning three league titles.
Beşiktaş are currently in the market for a new goalkeeper after a string of costly errors over the past two seasons from Tolga Zengin.
The keeper was blamed for the Black Eagles early exit from the Europa League in the group stages following their 3-1 defeat against Sporting Lisbon on the final match day.
