The Blades win means it now puts pressure on league leaders Preston North End and the rest of the chasing pack with two penalties and a late goal.
Ian Ross scored a brace while highly rated Jonathan Forte scored the late winner, both were born in the Steel City.
The team was a young side with the exception of Gary Kelly and Robert Ullathorne, although a welcome return was Iffy Onoura who made a second half appearance, this is first game at any level since his ligament damage that he picked up in a 1-0 victory over Rotherham United in September.
Ross first goal came when he missed his first penalty but he managed to find the rebound, though he confidently stepped up and inserted the second just after the break.
With 15 minutes left Nathan Joynes pulled one back for the Tykes but the visitors ended the game when Forte latched onto a Ross through ball to finish with style, a welcome goal as it was the hosts who were applying the pressure.
Barnsley: Ghent, Williams, Gibbs (Carrington 88), Dixon (Oldham 65), O'Callaghan, Hayward, Bertos, Rankin (Jones 45), Joynes, Gorre, Wroe. Unused: Parry, Baker.
Sheffield United: Kelly, Purkiss, Ullathorne, Ross, Cryan, K. Murphy, Hurst (Onoura 61), Tansley, Mallon, Killeen (Forte 78), Wood. Unused: Baum, Ellis, Sharp.
© Blades-Mad