Barnet will be the only non-league side in the FA Cup fourth round after beating Sheffield United – a team 84 places higher than them in the English football pyramid.
Shaquile Coulthirst converted from the spot after Richard Stearman brought down Ephron Mason-Clark to secure a 1-0 win at the Championship side.
Bees keeper Mark Cousins had to make a fine save late on to deny Leon Clarke.
But Barnet held on to reach the fourth round for the first time in 11 years.
The Bees had given their hosts an early scare when Coulthirst found the net, but the Tottenham academy product was offside when he headed home Cheye Alexander’s cross in the opening moments.
They almost doubled their lead early in the second half as Marvin Johnson had to make a telling intervention to divert Mason-Clark’s cross away from the awaiting Medy Elito, before Dan Sweeney failed to convert Elito’s corner from just a yard out minutes later.
Chris Wilder, who made 10 changes to his Blades starting XI, brought on captain and top scorer Billy Sharp after 65 minutes but even he could not break Barnet’s resistance.
The Bees, who sit 15th in the National League side, will now eagerly await Monday’s draw, in which they will discover their fourth round opponents.