Harrogate completed their first-ever Football League double thanks to Aaron Martin's sixth goal of the season.
wMartin's early second-half strike secured a 1-0 triumph for Simon Weaver's men - the same scoreline by which they defeated Mansfield at Field Mill in November.
The Stags provided the greater first-half goal threat with Ollie Clarke bursting into the box to call home keeper James Belshaw into early action.
The purposeful midfielder also saw a curling free-kick pushed behind by Belshaw, with centre-back Farrend Rawson heading inches wide from Jason Law's resulting corner.
But it was Martin who made the breakthrough just nine seconds after the interval when Rawson's headed clearance dropped to him 15 yards from goal and he aimed a perfectly-controlled volley into away keeper Aidan Stone's bottom right corner.
The goal settled Harrogate who saw Josh McPake fire just over from the edge of the box, while substitute Lloyd Kerry tested Stone from a similar distance.
Mansfield mustered little in response and have now suffered three consecutive league defeats, equalling their worst sequence since April 2018.