The Bulgarian fired in to level for Mark Hughes' side two minutes into the second half after Charles N'Zogbia had put the Latics in front in first half stoppage time.
City were made to hang on for the point which leaves them in sixth position when Pablo Zabaleta was sent off for two yellow cards with 25 minutes remaining at the DW Stadium. Wigan's first draw of the season leaves them in 13th position on 10 points.
The first half was virtually devoid of any real scoring opportunities and it took until the 38th minute for either goalkeeper to be really tested when Hugo Rodallega's stinging drive from 30 yards was parried by City shot-stopper Shay Given.
All the goalmouth action of the half featured in the last minute when N'Zogbia had an effort disallowed following great build up play by Jason Scotland to set him up when referee Alan Wiley deemed the Frenchman had tripped Gareth Barry before putting the ball into the net.
However the former Newcastle man was not to be denied a goal as he converted from close range in stoppage time when Given could only parry Rodallega's low drive from the left side of the area which was heading for the far corner of the net.
City were level within two minutes of the second half getting underway when Carlos Tevez's run and subsequent cross from the right flank ran through to Petrov on the edge of the area and he got the ball on to his left foot before firing low past Chris Kirkland.
On 53 minutes Titus Bramble's brilliant last-ditch tackle denied Emmanuel Adebayor a scoring chance, while Shaun Wright-Phillips' follow up effort was well saved by Kirkland.
Barry went close with a header from a tight angle which Kirkland parried across his own area on 64 minutes, just before Zabaleta's lunging foul on Scotland resulted in him being sent off for a second booking.
Wigan dominated possession with the extra man and Hendry Thomas had a goal ruled out for offside on 73 minutes, while Rodallega was denied by Given three minutes later.
City broke on 80 minutes and looked to have been denied a clear penalty when Wright-Phillips was brought down by Maynor Figueroa in the area, but the referee awarded a goal kick.
Wigan duo Jordi Gomez and Rodallega were both denied by Given in the final few minutes as City held on for a hard-fought share of the spoils.