Ayhan Bilgen, spokesman for the Peoples' Democratic Party, HDP, told The Associated Press that Buldan was taken away for questioning from her home in Istanbul early today.
The state-run Anadolu Agency said she was detained over an on-going investigation into her activities.
Turkey's government accuses the HDP, the nation's third-largest party, of links to the outlawed Kurdish rebels an accusation the party rejects.
In May, parliament voted to strip lawmakers of their legal immunity, paving the way for the HDP legislators' arrests.