The 20-year-old defender has penned a four-year deal, and revealed that he could have made the move to join the Jose Mourinho revolution at Stamford Bridge.
However, the Denmark international feels Villa were the team for him, and a talk with manager Paul Lambert was a decisive factor in his decision.
"I have a good feeling it was the right decision to turn down Chelsea," Okore told Sporten.dk.
"I feel that I have arrived at a club that believes in me.
"The manager has said all the right things and that has caught my attention. This is going to be good."
His former club FC Nordsjaelland are also very pleased with the deal, and delighted that a club like Villa are interested in their players.
"We are really proud of the fact that our huge investment on talent work is paying off with a huge transfer to the biggest league in the world," sporting director Jan Laursen told the club's website.
"Jores will now be a role model for all of our other talented players."