Paul Hurst made two changes to the team with Alex Rodman dropping to the bench and Lenell John-Lewis dropping out of the 16 man squad - replaced by Andy Cook and Scott Kerr.
Town lined up with Shaun Pearson Andrew Boyce, Aswad Thomas and Sam Hatton making up the back four, Craig Disley on the right side of a four man midfield, with Andi Thanoj and Scott in the centre of the park. Scott Neilson was given a left midfield role and Andy Cook and Connor Jennings were up front for Town.
The Mariners got off to the worst possible start when veteran striker Lee Hughes fired the home side ahead after just 2 minutes.
The former Notts County striker broke clear and galloped away down the right, before cutting inside and slotting the ball through James McKeown’s legs.
The Mariners survived another break after 10 minutes but this time some great last ditch defending by Sam Hatton prevented Hughes from doubling Rover’s lead.
On 22 minutes the Mariners got their first real sniff at goal. After some good work on the Town right the ball broke to Connor Jennings whose weak shot was easily covered by Russell in the Forest Green goal.
A well worked short corner was drilled in to Neilson but the midfielder, who had made himself some space in the box, saw his shot blocked.
Forest Green Rovers doubled their lead on 29 minutes when Oshodi rose the highest from a corner and bulleted his header past McKeown from close in.
But Andy Cook had a chance to reduce the arrears but the Town striker seemed to scuff his shot and Russell made a routine save.
Half Time: Forest Green Rovers 2 Grimsby Town 0
There was more urgency from the Mariners after the break and Sam Russell had to be alert tip over a header from Andy Cook.
The increasingly dangerous looking Scott Neilson had Russell beaten - but his fierce effort hit the post and went wide.
But Neilson was to trim Town’s deficit on 57 minutes. Scott Kerr’s short corner found its way to the Town man whose shot again hit the post but this time found it’s way over the line.
The home side nearly added a third though when Norwood’s touch from close in almost crept in at the far post.
Sam Hatton’s free kick almost drew Town level as the ball flicked off a Forest Green defender and went just wide.
Oumare Tounkara replaced Andy Cook on 72 minutes.
Ross Hannah replaced Scott Neilson and Patrick McLaughlin replaced Andi Thanoj as the Mariners looked to get vital equaliser.
Shaun Pearson almost snatched it after some great sustained pressure by Town. Connor Jennings teased his marker before delivering a great ball to the Town defender but unfortunately his header seemed to be deflected wide.
Despite the Mariners’ improved second half improvement, it was the two first half goal which did all the damage.