Memduh Cikmaz is accused of giving millions to the movement run by US-based Gulen, who Ankara claims ordered the July 15, 2016 attempt to end President Recep Tayyip Erdogan's rule.
Cikmaz was captured in a joint operation involving Sudanese intelligence after the Turkish National Intelligence Organisation (MIT) located him two months earlier, security sources told Anadolu news agency.
Cikmaz, with business interests in petrol stations and brick factories, was returned to Turkey early today, the agency said.
Cikmaz was accused of "managing an armed terror organisation" in a previous arrest warrant. Anadolu described him as the Gulen group's "money vault".
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The agency said MIT had created a special team to locate suspected Gulenists abroad.
Turkey refers to Gulen's group as the "Fethullah Terrorist Organisation" (FETO) but the movement insists it is peaceful and promotes education, denying any terror links.
Its network stretches from Turkey to Africa and Central Asia to the United States.
Gulen denies Turkey's accusations of involvement in last year's failed coup.
During high-level diplomatic visits, Ankara has also urged Pakistan and Tanzania to crackdown on the Gulen network, especially its schools.