The group, reported to be made up of three men, two women and four children, was held at Reyhanli, in Hatay province, near the Syrian border.
Their intention in travelling to the region, where Islamic State militants have carved out an area of control, was not immediately clear but there were fears they may have a terror-related intention. The UK foreign office said it is in contact with the Turkish authorities.
About 600 Britons are believed to have gone to Syria or Iraq since IS seized control of large swathes of territory there. Most are thought to have volunteered as fighters for the militant Islamist group.
Around half are believed to have later returned to the United Kingdom, Scotland Yard has said.
The latest detentions come two weeks after three British teenagers were stopped from travelling into Syria from Turkey.
The three -- two aged 17 and one 19, from north-west London -- were arrested following a tip-off from British police and flown back to the UK. They have since been released on bail.
They had flown to Turkey from Barcelona and were arrested at Sabiha Gokcen airport in Istanbul.
In February this year, there was tension between the British police and Turkish officials after three London schoolgirls disappeared from Turkey, apparently having crossed the border into Syria.
Shamima Begum, Amira Abase, both 15, and Kadiza Sultana, 16 had flown to Istanbul and travelled to the border region.
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