The 36-year-old striker and Blues favourite returns to Stamford Bridge after leaving in 2012 for stints at Shanghai Shenhua and Galatasaray.
“It was an easy decision — I couldn’t turn down the opportunity to work with Jose again,” Drogba said.
“Everyone knows the special relationship I have with this club and it has always felt like home to me.”
Drogba became a free agent upon leaving Galatasaray at the end of last season so there is no transfer fee involved.
The Ivorian marksman was named Chelsea’s greatest ever player in a poll of fans in 2012 after scoring 157 goals in 341 appearances.
His last act in a Blues shirt was to rifle home the winning penalty in the shoot-out against Bayern Munich that seized the London club’s only Champions League crown two years ago.
Mourinho, who originally lured Drogba to Chelsea for £24 million in 2004, insists the decision to re-sign the club’s fourth highest scorer of all time was not clouded by sentimentality.
“Didier’s coming because he’s one of the best strikers in Europe,” Mourinho said.
At Chelsea he joins a crop of strikers including new signing Diego Costa as well as Romelu Lukaku and Victor Moses, who both spent last season out on loan.
Samuel Eto’o and Demba Ba have already departed the club this summer.
Meanwhile, Manchester United look set to miss out on targets Arturo Vidal and Kevin Strootman.
Juventus and Chile midfielder Vidal has been closely linked with a big-money switch to United this summer but, according to reports in Italy, the 27-year-old has indicated his future is not with Louis van Gaal’s side.
Speaking on his return to Turin following a post-World Cup holiday, Vidal said: “Can I say that I stay at Juve? I do not know. I will talk with [new Juve coach Massimiliano] Allegri then we’ll see. I’m happy here. I have not yet spoken with Allegri and even with my friends, I do not go to Manchester.”
Roma manager Rudi Garcia, meanwhile, ruled out the possibility of Kevin Strootman leaving Roma for United.
United are believed to have bid at least £30m for the Holland midfielder. But Garcia insists the 24-year-old is going nowhere.
“Strootman is a Roma player. He will be a Roma player this year. There is no doubt about that,” Garcia said ahead of Roma’s friendly against United in Denver today (9.06pm Irish time).
One man who definitely won’t be at Old Trafford next year is Bebe. His nightmare spell at United finally come to an end yesterday after he was sold to Benfica. United paid Vitoria de Guimaraes £7.4m for the striker in 2010, but he only started three games — all in the cup competitions.
The 24-year-old, who made seven appearances in total, never looked like making it into the United first team and he was shipped out on loan to Besiktas, Rio Ave and Pacos de Ferreira.
Benfica yesterday confirmed the player had signed a four-year deal.
Sunderland head coach Gus Poyet yesterday signed Chelsea full-back Patrick van Aanholt after becoming frustrated in their pursuit of Fiorentina defender Marcos Alonso.
The Dutchman, who came through the ranks at Chelsea while Black Cats sporting director Lee Congerton was at the club, has spent the last two-and-a-half seasons on loan at Vitesse Arnhem.
West Ham co-chairman David Sullivan has confirmed the club are in the hunt for at least one new striker having again lost Andy Carroll to injury.
Club-record signing Carroll could miss up to four months after undergoing surgery on an ankle injury.
Hammers’ boss Sam Allardyce has already made moves to increase his attacking options with Mauro Zarate signed and Enner Valencia only needing a work permit to complete a move to Upton Park. But, with Carroll crocked once again, Sullivan insists adding even more firepower to their front line is now a priority.
“We have to bring in another striker and we’re working on it now to buy one, or loan one, or both,” he said.
“You can never have enough strikers and really with Andy gone we haven’t got enough. It was desperate last year... We probably made a mistake by putting all our eggs in one basket.”
Crystal Palace have announced the signing of striker Fraizer Campbell from Cardiff for an undisclosed fee on a three-year deal.