Rushden took all three points against Grimsby who must count themselves unfortunate after dominating the match for much of the game.
Grimsby started the game the better side and, on five minutes, Dean Gordon was inches over with his well struck free-kick. Jason Crowe then found himself in space for the visitors on 10 minutes but he shot weakly at keeper Billy Turley.
On 17 minutes Crowe was again in the thick of the action when he blasted over after a bad defensive mistake by Rushden.
Both sides found it hard to create clear-cut chances and both goalkeepers were rarely tested in the opening half-hour. On 34 minutes Ashley Sestanovich tested Turley with a long range effort.
The game followed much the same pattern in the second half with the visitors in control for much of the time and on 50 minutes Terry Fleming produced a fine save from Turley, whilst Crowe almost converted a cross after clever work by Andy Parkinson.
On 66 minutes the powerful Michael Reddy forced Turley to make another good save at the foot of his post.
In the 71st minute Rushden took the lead when following Stuart Gray's free-kick Andrew Burgess saw his shot blocked but the ball fell to Kevin Braniff 10 yards out and the on-loan striker from Millwall shot powerfully home leaving Anthony Williams helpless.
On 75 minutes Rushden almost increased their lead but a magnificent save by Williams denied Braniff.
Grimsby pressed forward in an attempt to get an equaliser but the Rushden defence held firm and the only scare came in the 84th minute when Turley brilliantly denied Thomas Pinault when his effort looked to be heading for the back of the net.