Ivanovic, 36, has signed a one-year contract with the Baggies and taken the number 20 shirt.
Welcome to West Bromwich Albion, Branislav Ivanović ✍️🇷🇸 pic.twitter.com/kXDjQpbmdm
— West Bromwich Albion (@WBA) September 15, 2020
He spent the last three-and-a-half years with Russian giants Zenit before leaving at the end of his contract.
Everton were linked with the experienced Serb, but he will link up with Slaven Bilic at West Brom instead.
In nine years at Chelsea, Ivanovic won three Premier League titles, the Champions League, Europa League, FA Cup and League Cup.
Ivanovic said he is happy to be back in England in his first interview as a West Brom player.
“The Premier League is the best league in the world,” said Ivanovic.
“I need to challenge myself and I am ready for the challenge. I’m really happy to be back playing in the Premier League.
“I hope I am going to be successful here.
“I have a lot of ambition and I want to prove a lot of things. I’ll give everything for the team.”