Buckley, who was appointed manager in midweek, will have been impressed by the way the lowly League Two outfit more than matched their higher division opponents despite being without a number of first-team regulars.
Grimsby had the better of the first half and, despite having to play second fiddle for long periods in the second period, Grimsby fully deserved a second bite of the cherry against a side they were fighting for promotion against last season.
Grimsby made a bright start and had several chances in the opening few minutes. Loan striker Danny North nipped on to a short back pass before rounding keeper Mark Bunn but defender Pedj Bojic was alert to the danger and rescued the situation.
Tom Newey then went close with a 25-yard shot which Bunn did well to tip away for a corner and Nick Fenton headed just over from the near post from Ciaran Toner's flag-kick.
Northampton rarely threatened despite the prompting of Eoin Jess in midfield. And it was Jess who had Northampton's only two chances of the opening half, curling a 20-yard effort wide in the 11th minute before snatching at another shot just before the break.
In between, North hit a first-time volley from Danny Boshell's cross which Bunn did well to save, while Newey saw his cross-shot sail just over the bar after linking up well with Nick Heggarty.
With Justin Whittle and Fenton solid in the centre of the Grimsby defence and Newey impressing alongside, Grimsby were never really stretched.
Despite only playing with North upfront they still created the better chances with Toner and Heggarty doing well on the flanks.
But it took a timely interception from Newey in first-half stoppage time by heading the ball clear for a corner from Jason Crowe's cross to deny Scott McGleish a certain goal at the far post following a rare attack from Northampton.
Northampton began the second half with more urgency and they created several chances early on.
All three fell to McGleish, who saw a 25-yard low drive go just wide, a rising shot fly just over the bar from a tight angle and a shot on the turn from close range go just wide of the upright.
But fellow striker Andy Kirk was ineffective up front, being well marshalled by skipper Whittle and Fenton.
It wasn't until the 75th minute that Grimsby keeper Phil Barnes was seriously tested as he did well to keep out a close-range effort from Chris Doig. From the ensuing corner Andy Holt saw his header cleared off the line by Fenton.
For Northampton it was too little too late and despite their pressure in the closing stages it was Grimsby who nearly nicked it.
Gary Harkins tested Bunn from 25 yards and in the closing stages a quick break by the visitors ended with North cutting into the area but the striker was unable to beat Bunn who dealt comfortably with his attempted chip.