Roberto Mancini’s side looked set to fall four points behind city rivals Manchester United at the summit of the table when Gary Cahill scored a deflected opening goal for Chelsea on the hour mark, but his Argentina strikers had other ideas as they helped haul City back from the brink of a bruising defeat.
Sergio Aguero netted a penalty on 78 minutes after Michael Essien was deemed to have handled in the box before Tevez – on for Nigel De Jong after 66 minutes – slipped the ball into the path of Nasri to chip Petr Cech for the winning goal on 85 minutes as scenes of euphoria engulfed the stadium.
It was Tevez's first appearance for City six months after he infamously refused to warm-up during a Champions League match at Bayern Munich.
City are now only a point behind leaders United after a 20th straight league win at home - a record for the Premier League - with nine games left. They last sampled a loss at home in the Premier League to Everton some 15 months ago.
How they escaped with three points here was a minor miracle with Chelsea proving stubborn opponents for much of the night under their caretaker boss Roberto Di Matteo, who tasted his first defeat as manager of the London side since replacing the sacked Andre Villas-Boas earlier this month.
City carved out the first chance of the evening when Pablo Zabaleta slipped the ball to David Silva, who knocked a shot over the bar before Juan Mata did likewise at the other end by ballooning an effort over from Fernando Torres's pass.
Nasri was desperately unfortunate to hit the bar with Cech beaten from his shot on 11 minutes while Mario Balotelli should have scored on 29 minutes when he was presented with the ball by Frank Lampard, but he could only knock a shot wide of goal with Cech getting a glove to his effort.
City opted to wheel on Gareth Barry at half-time for Balotelli with Chelsea having the misfortune of losing the injured Branislav Ivanovic midway through the first period.
Nasri hit the bar for a second time in the contest with Cech tipping his cross onto the woodwork on 56 minutes before the visiting team struck the opening goal with one of their rare attacking moments in the second half.
Cahill saw a hopeful shot deflect off Yaya Toure before spinning beyond the England goalkeeper Joe Hart, who could not recover as the ball deflected beyond him low to his left. It was Cahill's first league goal for the club.
Chelsea were forced to hit on the break by this stage, but were undone just when they seemed to have done the hard part. Zabaleta drove a shot at the substitute Essien, a replacement for Raul Meireles, who had no complaints after referee Mike Dean penalised him for lifting his arms in the area.
Aguero sent Cech the wrong way from the penalty spot before Nasri clipped the winner into the net seconds after Cech had held a blistering shot by the vibrant home midfielder.
The win was all the more vital after City lost at Swansea 10 days ago. They will move two points clear of United at the top of standings if they win at Stoke City on Saturday before their city foes host Fulham at Old Trafford on Monday evening.