The 36-year-old former England midfielder, who announced his international retirement last month, levelled five minutes before the end after man of the match James Milner had laid on perfectly.
Lampard scored 211 times in 648 appearances for the Stamford Bridge side but joined the Citizens on loan from MLS outfit New York City this summer.
Man of the Match Milner celebrates with goalscorer Lampard
And in his 78th-minute appearance, which was met with cheers from both sets of supporters, he grabbed his first for ten-man City who were trailing to Andre Schurrle's 71st-minute opener.
Lampard has now scored against 39 Premier League clubs, setting a Premier League record after moving one ahead of Andrew Cole.
While the home fans raised the roof when Lampard smashed home Milner's pass, the ex-Blues favourite refused to celebrate as his strike ended the Premier League leaders' 100 per cent record. England's Gary Cahill was on show for Chelsea, while Joe Hart kept goal for Manchester City.
At Goodison Park, Leighton Baines scored a late penalty for Everton against Crystal Palace, but it couldn't stop the visitors - inspired by Yannick Bolasie - from a smash-and-grab raid for their first win of the season.
The Congo winger capped a fine display scoring the Eagles' final goal in the 69th minute to secure a 3-2 victory. Romelu Lukaku had given Everton a ninth-minute lead, but Mile Jedinak equalised from the spot and Fraizer Campbell took advantage of an error by Tim Howard to change the course of the game.
Lukaku and Phil Jagielka both came close for Everton, who also had John Stones in defence, during a frantic finale but Palace held on.
Leighton Baines tucks away a late penalty against Palace
England captain Wayne Rooney looked to be heading for victory with his Manchester United side at Leicester City after Robin van Persie and Angel di Maria had given them a 2-0 lead inside 16 minutes.
Leonardo Ulloa pulled one back almost instant, but Ander Herrera extended United's lead once again 12 minutes after the break.
However, the visitors, who featured England Under-21s defender Tyler Blackett at centre-back alongside Chris Smalling - coming on for the injured Jonny Evans on the half-hour mark, were stunned by a remarkable turn-around by the Premier League new boys.
David Nugent - who scored one goal for England in his only senior appearance in Andorra seven years ago - netted from the penalty spot before Argentinian midfielder Esteban Cambiasso squared the contest.
Man of the match Jamie Vardy edged Nigel Pearson's side into the lead with a fine finish stroking past David de Gea and another penalty - this time from Ulloa after Blackett was sent-off for a foul on Vardy inside the box - clinched a memorable Foxes win.
Danny Rose and Eric Dier could do nothing to prevent West Bromwich Albion from victory over Tottenham Hotspur at White Hart Lane.
Scotland midfielder James Morrison got only goal of the game with a second-half header, while Spurs were frustrated by brilliant Joleon Lescott defending on his Baggies debut.
Under-21s striker Saido Berahino started up front for West Brom, coming close with two efforts, while Three Lions keeper Ben Foster kept a clean-sheet in the victory.
England's next game is against San Marino at Wembley Stadium on Thursday 9 October. Tickets are available to buy online from www.TheFA.com/tickets.
Ticket prices: £25, £35, £45 & £55 (Family enclosure - £20 adults/£10 children under 16)
A £10 discount is available for OAPSs, students and U16s elsewhere in the stadium
Hotline: 0844 826 2010
General public disabled sale hotline: 0845 458 1966
