Both clubs have confirmed the deal, with the Turkish side reportedly meeting a €5million exit clause in the striker's contract, with only final personal terms and a medical left before the transfer is completed.
Soldado is due to arrive in Istanbul on Wednesday evening, where negotiations will continue, but Fener say he has agreed to the switch in principle.
Road to Istambul pic.twitter.com/VcJwCjqpaa— Roberto Soldado (@R9Soldado) August 9, 2017
Soldado has spent two seasons with Villarreal, who he joined following an unsuccessful spell in the Premier League with Tottenham.
The 32-year-old only scored nine league goals in the last two campaigns and was restricted to 10 top-flight appearances last season due to an ACL injury.