A last-gasp winner from Sergio Aguero against QPR on the final day of the season sealed City's first title in 44 years, sparking scenes of euphoria at the Etihad Stadium.
The 47-year-old Italian says that the hard work begins now as defending champions, and is asking his players to work harder than ever to preserve that status.
"We must always be looking to work harder and to keep improving," Mancini told FA.com.
"We are determined to hold on to the trophy that we won in May but we know that we cannot rest on that success or start thinking that, because we won the title, we are the best or have a right to win again.
"We start again at home against Southampton as if from nothing; we must forget that we won the title. Every team will want to beat us and now we must work harder than ever before."
Mancini's men take on Chelsea at Villa Park in the Community Shield, the annual pre-cursor to the league season, and the Italian is looking for a different outcome this time round after defeat to Manchester United last year.
"We are delighted to be back in The Community Shield," he continued, "not least because if you are playing in the game then it means you have been successful the previous season.
"It should be a great occasion as it was last year against Manchester United, though of course we hope for a different outcome this time.
"Chelsea is a great club and will be difficult opponents. I am sure both our clubs will be involved closely in the title race this season.
"This game is where it all comes together for both us and Chelsea."