The nine were taken by minibus from custody cells in the Hatay region of south Turkey on the Syrian border to the city of of Adana where they were put on a flight to the Mediterranean city of Antalya, the Anatolia news agency said.
From Antalya, they were then put on another flight back to Britain.
The nine had been arrested on April 1 and their case generated huge attention after it emerged that the group included four children and the son of a British local politician.
Turkey has in the last months been repeatedly criticised by its Western allies for not doing enough to halt the flow across Turkish territory of European nationals seeking to join IS jihadists in Syria.
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However it has made a number of arrests in recent months in an apparent bid to deflect the criticism and insists it is doing all it can to control the border.
The deportation of the nine back to Britain took much longer than expected.