"Champions! What a terrific feeling! So happy to be able to share another trophy with our awesome fans!"
Mourinho lambasted his players for over-elaborating in possession, calling them "masters of complication", after they produced a performance completely at odds with the stirring second-half showing in their 3-2 title-delaying victory against City last week.
United had beaten City in a stunning comeback during the derby, denying them the title, but denied that win was the most important win of the season.
"With my experience you don't titles with inconsistency".
And they can thank fierce rival Manchester United for that.
"We're all winners and we want to win and in those games unfortunately we didn't. Premier League Champions 17/18", City tweeted soon after the final whistle.
"You can't take (winning the league) for granted, I've won three now but there's so many we've missed", he said.
"You see the difference of attitude of some players today compared with other weeks; relax, too stylish, one more touch, one more turn, one more flick".
"I'm not going to stand here and say we didn't deserve what happened", he added.
Mourinho also blamed United's overcomplicated play on their defeat to bottom-side West Brom.
City have won the title with five games to spare, equalling the English top-flight record which was first set by United in 1907-08.
"We did it! An unbelievable journey to get here".
City manager Pep Guardiola might have rubbed his eyes in disbelief at events at Old Trafford when he returned from his round of golf with his son. "Very happy to call us champions this year!"
United pushed numbers forward in the closing stages, but Foster never really looked in danger of being tested again as United succumbed to a defeat that was celebrated by the blue half of Manchester with even more vigour than usual.
A serial victor as a supervisor with Barcelona and Barcelona, Guardiola ended his first yr in England at Metropolis with out silverware - his exclusively failure to win a trophy since his managerial profession began again in 2007.
It's the third Premier League success for the club after the titles won in 2012 under Roberto Mancini and 2014 under Manuel Pellegrini with captain Vincent Kompany, David Silva, Sergio Aguero and Yaya Toure involved in all of them.