The Mariners, urged on by more than 1,000 travelling fans, always had a slight edge even when Notts raised their game in the second half.
Two of those who looked most competent for Town were ex-Magpies star Paul Bolland, who starred in midfield, and goalkeeper Steve Mildenhall who should have been given far more work to do.
A classic example of this came in the 37th minute when Notts worked a nice move to release Mike Edwards in the inside left channel but his left-foot volley flew wide of the target when Mildenhall should have been tested.
Grimsby, on the other hand, applied ruthless efficiency when an opportunity came their way three minutes later, although Notts felt it should have been ruled offside.
It was effective route one football as defender Tom Newey released a glorious 40-yard pass into the path of Michael Reddy who controlled it superbly and drilled a low shot past a helpless Kevin Pilkington.
It was Reddy's 12th goal of the season and he proved a constant threat to the Notts defence.
Mildenhall's one moment of real anxiety came in the second half when Eugene Dadi flicked on a set-piece into the path of Julien Baudet inside the six-yard box, and he jabbed it towards goal.
Mildenhall, riding his luck, first sat on the ball and then smothered it - and with it went Notts' hopes of saving a point as they headed to their first defeat in four matches and their first at Meadow Lane in seven.