The 34-year old former Barcelona man moved to the Stade Louis II last year and on Thursday agreed a new one-year deal with the last season's Ligue 1 runners-up.
However, Abidal will move to the Karaiskakis Stadium after Olympiacos confirmed his arrival on their official website.
"Olympiacos announces the acquisition [of] the player Eric Abidal from Monaco," they stated.
Abidal, who was a regular in all competitions for Monaco last season under Claudio Ranieri, will link up with former France international Christian Karembeu in the Greek capital.
Karembeu holds an advisory role with the club, managed by Michel, and was reported to be a key figure in bringing Abidal in.
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