A source close to the club told Turkish-football.com that Besiktas will pay the Blues a €700,000 loan fee and have a €3 million release clause option which will remain active until the end of the season.
There will now be a total of 22 Nigerian players plying there trade in Turkey – all leagues.
Omeruo was also one of the 35 players the Blues loaned out last season, playing for Super Lig minnows Kasimpasa.
The 22-year-old was however, won of the stand out young defenders in the league making 25 Super Lig appearances.
Omeruo earned himself an upgrade across Istanbul to league giants Besiktas where he will gain Champions League football experience for the first time in his career.
Chelsea currently have one player loaned out in Turkey but did also have Marko Marin at Trabzonspor last season.
Besiktas are keen on loaning Loic Remy as well from the London based outfit but have yet to reach an agreement.