Yeovil went into the game having collected six goals and maximum points in their two previous away matches, but at Huish Park there was a repeat of the goalless stalemate that had launched their Christmas programme against Bradford City.
Yeovil were without their inspirational skipper Terry Skiverton, but Northampton also had stars missing, notably Scott McGleish and defender Sean Dyche.
It was the visitors who looked the more dangerous early on and in the 19th minute Mildenhall made a fantastic save to prevent Ian Taylor from opening the scoring. He got his chance when both Nathan Jones and Terrell Forbes mis-kicked when trying to clear.
Mildenhall was busy throughout the half and saved well again from Eoin Jess before Yeovil brought the best out of visiting keeper Mark Bunn.
His best work in the first half came when the talented Lee Morris back heeled and loanee Martin Cranie fired a low shot from the edge of the box which Bunn saved expertly.
Yeovil began the second half in much brighter vain. Arron Davies curled one shot just wide and Cranie put a header from a corner just over the bar.
Leon Best, who has been scoring regularly since moving from Southampton on loan, also came close to breaking the deadlock on 66 minutes bringin a great save from Bunn.
But it was Mildenhall who earned the final plaudits. In the 71st and 83rd minutes he made two more excellent saves, both from substitute Brett Johnson.
There was a double blow for Yeovil on the booking front. Left-back Jones, who took over from the injured Skiverton as captain for the day, was yellow-carded for a 35th minute foul.
That was his fifth of the season and he will miss a trip to promotion favourites Nottingham Forest. Near the end, midfielder Chris Cohen was also shown the yellow card for the fifth time so he will also miss that crunch game.
Northampton also picked up a couple of bookings with Taylor fortunate to stay on after a cynical late foul which brought the dissent from Cohen that got him into trouble.