Grimsby player-manager Paul Groves hailed Marcel Cas and Michael Boulding as they combined twice in the last seven minutes to give the Mariners an impressive away win.
Brentford looked set to claim a draw even though Stephen Hunt's penalty had been cancelled out by Iffy Onuora just before half-time.
But winger Cas came off the bench to set Boulding up in the 84th and 88th minutes as Grimsby netted two late goals to snatch all three points.
Groves said: "Boulding's two goals were superbly taken. The first one was behind him, but it went in like a rocket.
"The second one was one-on-one and in training he strokes those away on a regular basis, so as soon as he was behind the last man I backed him to score.
"But Marcel Cas has changed the game. If the game is opening up and there is grass to run into then he is always going to cause problems with his pace and athleticism.
"I am delighted we have come from behind to win because that shows character and we all knew how big a game this was." Brentford started much the stronger and deservedly took the lead after just 10 minutes when John McDermott handled inside the area to allow Hunt to convert his sixth penalty of the season.
Grimsby struggled to make an impact, but just a minute before the break they took advantage of some sloppy defending as Onuora powered home a McDermott cross.
The second half was less exciting and the match looked to be heading for a draw until substitute Cas raced 50 yards clear after Brentford had made a hash of their own corner and squared for Boulding to smash home.
And the striker netted his 12th of the season with a cool finish near the death as he converted past goalkeeper Paul Smith after being sent clear by Cas.
Brentford manager Wally Downes complained: "We gifted them the game by making a mistake at our own corner and then defended poorly in the build up to their second goal.
"I'm not the kind of guy that likes to hang on for a draw and I think we had a responsibility to push forward for the winner.
"However, sometimes when you do that you get punished and that's what happened today. At 1-1 whoever scored the next goal was likely to win.
"I don't think we played badly overall, but in an ideal world we would have put away the goals in the first half when we were on top and then seen out the second half. Unfortunately, life doesn't always work out the way you want it."