The Dutchman’s time at the north London club looks set to come to an end after the club confirmed that he is no longer the number nine.
Janssen spent last season on loan in the Turkish Super Lig with Fenerbahce and was linked with a move back there, but they opted to sign Islam Slimani from Leicester City.
However, Galatasaray are looking for a striker and have been keeping an eye on the situation of Janssen, who has fallen heavily out of favour under Mauricio Pochettino.
The 24-year-old joined Spurs for £17m in 2016 but has only managed to score one Premier League goal since.
Janssen managed to find the back of the net four times in the Turkish top flight last season and Galatasaray are hoping that they can help him to rediscover the form that led Spurs to sign him.