Struggling Lincoln picked up their first point of the season thanks to a second-half fightback.
Lincoln goalkeeper Rob Burch had no chance when Peter Till fired home a left-foot shot in the 38th minute, after some slack defending.
A Lenny John Lewis header just before half time almost pulled City level just before the break.
Ciy escaped on the hour when defender Frank Sinclair headed a clearance against his own crossbar, and shortly after Ben Wright thought he'd levelled for City only for his effort to be ruled offside for a second consecutive home game.
But they levelled in the 73rd minute after debutant Sam Mullarkey was fouled by Tom Newey and Lee Frecklington sent Phil Barnes the wrong way from the spot.
In truth a draw was more than Lincoln deserved as Grimsby wasted a plethora of chances, but it could have gone either way. On this form neither side will be troubling the play off spots.
The game was marred slightly by some Grimsby Town fans invading the pitch and attempting to attack Imps fans in the Stacey West, but the incident was dealt with excellently by stewards.