Atilla Selek was detained in the central Anatolian city of Konya on charges of membership in a terrorist organization and preparing to carry out bomb attacks, with the aim of extraditing him to Germany, police said in a statement.
Selek's lawyer, Manfred Gnjidic, on Tuesday said the arrest was connected to an alleged terrorist plot that German authorities foiled in September.
"He has nothing to do with it," Gnjidic said, adding that his client had traveled to Turkey months before the plot was foiled.
Two German converts to Islam and a Turk were arrested in Germany in September, accused of planning massive bombings against U.S. and other facilities in Germany.
German authorities have said that a militant group, the Islamic Jihad Union, claimed responsibility for the plot, and that the targets were the U.S. air base at Ramstein and U.S. and Uzbek consular facilities in Germany.
The German daily Sueddeutsche Zeitung, which did not cite its sources, reported that Selek is accused of membership in a terrorist organization and allegedly helped the group acquire detonators.
Selek, 22, is a German citizen.