It proved a frustrating night at Eastlands for City as Everton triumphed to keep alive their hopes of pinching a place in the Europa League.
Goals from Tom Cahill and Mikel Arteta moved Everton to within three points of their Merseyside neighbours Liverpool as they continue their end-of-season charge up the table.
And the defeat heaps further pressure on Mancini to deliver a top-four finish to qualify for Europe's top club competition.
After a low-key opening, City began to take control putting the Everton defence under intense pressure.
Everton were indebted to Tim Howard who made two important saves in the opening 25 minutes to keep City at bay.
First he stretched to catch Micah Richards' header under the crossbar and then he dived bravely at the feet of Carlos Tevez as the visitors were in danger of being overwhelmed.
Then, completely against the run of play, Everton stole ahead in the 33rd minute when Cahill glanced home a header from a Leighton Baines cross which followed a short free-kick by Arteta.
Everton had two great chances to double their lead early in the second half but Leon Osman's shot was deflected by defender Vincent Kompany for a corner and then Cahill's chip flew agonisingly wide.
City threw on Roque Santa Cruz and Patrick Vieira in the second half but they were unable to transform the home side's fortunes as Everton defended resolutely to hold on to their lead.
Everton sealed victory five minutes from time when substitute Jack Rodwell made a terrific break down the right.
Cahill stepped over his low cross and Arteta fired low past keeper Shay Given for his fourth goal of the season.
Mancini's frustration boiled over in stoppage time when he was sent off by referee Peter Walton following a bust up with Everton manager David Moyes in the technical area as he retrieved the ball which had gone out of play.
Source: DSG
