The 23-year-old only arrived on Wearside in January - signed up by Martin O'Neill in a £3.8million deal from Bursaspor - but has failed to make a significant impression on new boss Paolo Di Canio.
Eskisehirspor manager Ertugrul Saglam, who managed N'Diaye previously at Bursaspor, has moved quickly for the former France Under-21 star, who managed 16 appearances during his spell at the Stadium of Light.
The Sunderland website confirmed: "Alfred N'Diaye has joined Eskisehirspor on a season-long loan. The 23-year-old returns to Turkey having arrived at the Stadium of Light from Bursaspor during the January transfer window."
Di Canio has already bolstered his squad with no less than nine summer signings - and is reportedly closing in on the capture of Greek winger Charis Mavrias of Panathinaikos.