The man, named as Joseph A R, was detained in the Aegean holiday resort town of Didim in Aydin province and then remanded in custody by a court ahead of trial, the state-run Anadolu news agency said late today.
A Bulgarian citizen was detained with him but she was later allowed by the court to go free under judicial control. Her mother was also detained but freed without charge.
Ankara considers the YPG a terrorist group and the Syrian branch of the Kurdistan Workers' Party (PKK), which has waged an insurgency inside Turkey since 1984.
But Washington considers the YPG as the main fighting force on the ground in Syria against the Islamic State group.
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The United States is now openly arming the YPG and the group is heavily involved in the US-backed operation to oust IS jihadists from their stronghold of Raqa.
The BBC said the man is ex-soldier Joe Robinson, 24, from the northern English city of Leeds and the Bulgarian his fiance Mira Rojkan.
It said Robinson, who is originally from Lancashire, spent five months fighting as a volunteer with the YPG against IS. He had previously described his experiences in media interviews, including with the Guardian.
Anadolu said that Turkish police launched the raid to arrest him after receiving a tip-of by email.