31-year-old Chadli has inked a two-year contract with the Turkish champions and taken the number 11 shirt.
✍ 🔊 🎵🎶 🎼 pic.twitter.com/Q7Dst0aQYY
— İstanbul Başakşehir (@ibfk2014) September 10, 2020
Chadli had been keen on a return to Belgium, but has been given the chance to play Champions League football with Basaksehir.
The former Tottenham star joined Monaco in 2018, making 16 league appearances in his first year there.
Last season, he went to Anderlecht on loan, scoring eight goals and making five assists in 19 games.
Chadli has played 59 times for Belgium and represented them at both the 2014 and 2018 World Cups.
He is Basaksehir’s second signing from Ligue 1 in a matter of days after they recruited Rafael from Lyon.
Monaco have now sold, loaned or released 13 players this summer as part of Niko Kovac’s squad overhaul at the principality club.