The 36-year-old has joined the Baggies for a loose after his contract with Russian club Zenit St Petersburg expired.
SunSport reported last week how the former Chelsea star is about to move to the Hawthorns.
And now the club has shown its arrival, the Serbian alien dressed in the number 20 shirt.
Ivanovic, who returned to the Premier League after his departure in February 2017, spoke of his bond with Slaven Bilic’s men.
He told the club’s website: “The Premier League is the league of the world.
“I want to challenge myself and I’m in a position for the challenge. I am pleased to play again in the Premier League.
“I hope to be here.
“I have a lot of ambition and I need to do a lot of things. I’ll give it my all for the team. “
Bilic welcomed Ivanovic’s acquisition, as he said his delight would be invaluable to the newly promoted team.
He said: “It’s an addition to us, a newly promoted team in the Premier League. He meets all the requirements for us.
“He’s done everything in his career, he’s been magnificent. We’re excited. Add quality and delight on and off the field. “
“So it’s not just him, it’s more the influence he’s going to have, not just the defenders, but the whole team around him. “
“That’s why we targeted it as one of our main goals. It’s a signing for us. “
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