His destination was preordained, off to replace the "dead man walking" at Chelsea, the likeable Claudio Ranieri, who was sacked within days of leading the Blues to a second-placed finish and a semi-final place in the Champions League.
Mourinho had grabbed the Premier League's attention when sprinting down the Old Trafford touchline in the last 16, and interest was piqued even more when he famously pronounced himself "The Special One" during his first news conference as Chelsea boss.
Loved and loathed in almost equal measures, Mourinho was a gust of fresh air who swept through the English top flight, delivering Chelsea's first title win in 50 years on this day 15 years ago.
Here's how he did it.
Building on firm foundations
Chelsea had been ensconced in the top six of the Premier League for nigh on a decade by the time Mourinho arrived. With Roman Abramovich in the corridors of power Chelsea had thrown money at the team 12 months earlier, with Ranieri making some key signings in Joe Cole, Damien Duff and Claude Makelele.
What was lacking, it was felt, was a coach with the swagger and the genius to turn a good side into champions. A "special" coach.
Arsenal had won the previous season while going unbeaten and Mourinho made some big signings of his own to take them on.
Petr Cech, Didier Drogba, Ricardo Carvalho and Arjen Robben - to name half of his summer additions - would all play a huge part in the crushing title win.
And it was a procession in the end. Chelsea won 29 of their 38 Premier League games - losing just once - and incredibly conceding just 15 goals.
