Shrewsbury secured a play-off place after drawing with Grimsby in their last league match at Gay Meadow.
The Shrews fell behind when Andy Cooke lost possession and Grimsby capitalised with Andy Taylor scoring from 15 yards.
The hosts equalised when Ben Davies was bundled over in the box and converted the penalty and then Kelvin Langmead headed in Davies free-kick soon after.
But they were denied a win when Nick Fenton headed in Peter Till's last-gasp corner to hand the Mariners a draw.
Shrewsbury: Shearer, Luke Jones, Langmead, Hope (Fortune-West 59), Tierney, Davies, Edwards, Drummond, Ashton, Cooke, Asamoah (Burton 82).
Subs Not Used: MacKenzie, Humphrey, Symes.
Goals: Davies 63 pen, Langmead 74.
Grimsby: Barnes, McDermott (Whittle 73), Bennett, Fenton, Newey, Till, Bolland, Boshell, Toner, Jones, Taylor (Bore 63).
Subs Not Used: Murray, Hegarty, Bloomer.
Goals: Taylor 29, Fenton 90.
Ref: G Laws (Tyne & Wear).