The news came less than three hours before last night's Premier League encounter with Everton at Eastlands.
And although City could not make the most of their good fortune, losing 2-1 and missing the chance to secure top spot at Christmas for the first time since 1929, the elation in the Blues camp was obvious.
With his 10 goals already this season, Tevez has become a key figure in City's challenge for silverware.
Shooting star: Carlos Tevez has weighed in with 10 goals this season
And Mancini is adamant City can now look forward with renewed vigour.
'Carlos is a world class player whose contribution since he joined the club has been invaluable,' said the Italian.
'I am pleased that we are now able to focus on pure football matters and are able to look forward to Carlos continuing to play a significant role in the club's progress.'
Mancini also ensured Tevez kept the captaincy last night, something that looked highly unlikely until his abrupt U-turn.
Given all the bad blood between the two parties over the previous eight days, since the South American's desire to quit first became public knowledge, the truce was as startling as it was sudden.
Apparently, it came after a direct intervention from chairman Khaldoon al-Mubarak, who met with Tevez on Sunday, before further talks that included chief executive Garry Cook.
Pulling in the right direction: Roberto Mancini is delighted to have Tevez on board
Enough common ground was found for Tevez to withdraw his transfer request, even though it had been claimed part of his reason for wanting to quit was because of his family, who are back home in Argentina after being unable to settle in the UK.
Tevez also appears to have put to one side his relationships with Cook and director of football development Brian Marwood, which he had claimed were broken 'beyond repair'.
'It is very important for everyone; the club, the squad, for him,' said Mancini.
'The situation has been cleared up and everything has gone in a good way. It was important that we stopped talking about this situation. We are happy about that.
'It was important news but it was the only good news to come out of the night.'
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