The Senegal international is undergoing a medical with Rafa Benitez's side after a release clause was triggered in his Newcastle contract once Chelsea offered £7million for him.
Ba 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.
A deal between the Premier League rivals appears close to being finalised, with Benitez keen to add to his attacking options to ease the burden on Fernando Torres.
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 ahead of their defeat by Everton.
"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."