"I am very happy to join Basel, it's a step forward in my career," Ivanov, who signed a three-year contract, told local media. The deal includes an option for one more year.
The 25-year-old centre back, capped 35 times by the Balkan country, joined Partizan from Russia's Alania Vladikavkaz in 2011 and also had a successful spell at CSKA Sofia. He won two Serbian league title with the Belgrade-based side.
Basel blew a three-goal lead but hung on to beat Maccabi Tel Aviv 4-3 on aggregate on Tuesday to seal a place in the Champions League playoffs.
Ivanov will not be eligible to play for Basel in the playoffs having already played for Partizan in the Champions League's qualifying rounds.
(Reporting by Angel Krasimirov, editing by Amlan Chakraborty)
