Peterborough lost their 100 per cent away record against a Grimsby side battling against injury and suspension.
The visitors led from the 17th minute when Adam Newton's curling shot deceived Grimsby keeper Aidan Davison who failed to react.
Barry Fry's boys had the chances to extend their lead in the first half against a Grimsby side who failed to find any rhythm.
But it took a fine stop from Davison to deny David Farrell before striker Jonathan Rowan headed over with Grimsby's only goal attempt in the first half.
There had to be an improvement from the Mariners after the break and they pushed Boro back although keeper Mark Tyler was not called into serious action.
And just when it looked as if Grimsby were going down to their second home defeat in three games they equalised with ten minutes left.
A long ball out of defence from left back Mike Edwards, who was making his debut, found leading scorer Michael Boulding and the striker still had a lot of work to do before slipping the ball past Tyler.
Urged on by their fans Grimsby pressed for a winner but that would have been rough justice on battling Boro.
Boro boss Fry admitted afterwards that he had seriously considered wholesale changes following a third successive home defeat against Stockport but he praised his players especially for their first-half display.
"It was a huge disappointment to finish with only a point," he said. "We did brilliantly in the first half and were disappointed not to have been two or three up at half time when the game should have been over." Fry admitted that Grimsby came at his side a bit in the second half and was disappointed that the equaliser came with a move from one end of the pitch to the other.