The Senegal international is undergoing a medical with the European champions after a release clause was triggered in his Newcastle contract once Chelsea offered £7million.
He was left out of the Magpies' squad for their 2-1 home defeat to Everton on Wednesday, with manager Alan Pardew admitting afterwards that he was on his way to Stamford Bridge.
Ba joined Newcastle on a free transfer from West Ham in June 2011 and after impressing last season he has already scored 13 goals this campaign.
"It's done. He will go to Chelsea with our blessing," Pardew told Sky Sports on Wednesday.
"He has done fantastic for us and it's not a bad thing, all the uncertainty is now done and we can move on.
"The ball was always in Demba's court. But this club is bigger than any player for sure."
Chelsea officials held initial discussions with Ba's representatives earlier this week but had been unable to reach an agreement.
Newcastle released a statement which read: "Newcastle United can confirm Chelsea Football Club has made an official offer for Demba Ba which has triggered the release clause in the player's contract.
"The club has given the player permission to speak to Chelsea FC and therefore he will not be included in the squad for tonight's game with Everton."