Janssen came close to leaving Spurs for Brighton ahead of the English deadline last week, only for the proposed move to fail to materialise late in the day.
The deal has not yet been finalised, but Fenerbahce state that terms with both Spurs and the player have been agreed 'in principle'. As such, 23-year-old Janssen is due to arrive at Istanbul's Ataturk Airport at 12.30pm local time to continue the final negotiations.
As is often the case for high profile signings in Turkey, he is likely to greeted at the airport by hundreds of excited fans.
Fenerbahce's deal for Janssen appears to have come after failing to land Chelsea outcast Diego Costa, who appears set to re-sign with former club Atletico Madrid in January.
In Turkey, Janssen will join international colleague and two-time Premier League Golden Boot winner Robin van Persie, as well as another former Spurs flop in Roberto Soldado.