Max Watters headed the Tykes in front in the first half, but the Hornets equalised courtesy of Shamir Fenelon’s spectacular finish.
James Hammond’s spot-kick then stunned Oakwell, but Fabio Jalo’s fabulous curling effort saw the hosts level on the stroke of half-time.
Mael De Gevigney headed Barnsley in front again in the second half. The Tykes then wasted a hatful of chances to put the tie to bed before second half Horsham substitute Tom Richards tapped into an empty net following a lightning Hornets counter attack.
The two sides will meet again at the Camping World Community Stadium on Tuesday, November 14.
Here is a selection of excellent photos from Oakwell courtesy of Natalie Mayhew, ButterflyFootie.