The Championship winners have beaten off a host of competition to seal the Nigeria international's signature, and the 32-year-old is "very happy" to have joined the Bluebirds
The Nigerian forward had been linked with moves to Swansea and Stoke during the transfer window but Malky Mackay has won the race for the 32-year-old, who has signed a two-year deal.
Odemwingie becomes Cardiff's eighth new signing since their promotion to the Premier League and will provide added firepower, having scored 30 goals in his three-year spell at the Hawthorns.
|2/1||Cardiff are 2/1 with BetVictor to be relegated
"Peter completed his medical on Monday afternoon and will link up with his new team-mates later this week."
Odemwingie had fallen out of favour at West Brom after he tried to force through a move to QPR in January, and he is pleased to have been given the chance to make a "fresh start" with the Premier League new boys.
"I'm delighted to complete my move to Cardiff City. I'm looking forward to this fresh start at a club that is really going places, a team that's progressing fast," Odemwingie told the club's website.
"My father-in-law is a City fan and he's told me what a great club this is. I'm looking forward to meeting up with the boys and then start preparing for the trip to Hull after the international break.
"I've seen a little bit of the city and I know that my wife and I will really enjoy living in Cardiff. I can't wait to get started - this move makes me very happy."