Rob Atkinson scored first for the Reds after 12 minutes.
The Reds conceded a penalty on 39 minutes after Neil Austin tugged back Jack Lester in the area. David Scarsella kicked away his Lester's poor spot kick.
However, the Blades equalised on 44 minutes through Billy Sharp.
Reds midfielder marked his return from injury with a red card for dissent just before the half-time whistle.
United took the lead on 56 minutes through Kevan Hurst but a minute later the referee ralso reduced the Blades to 10 men when he showed Kyle McFadzean a straight red card after an incident involving Fola Onibuje.
Tom Baker equalised for the Reds aafter 70 minutes after good work by Mark Stallard.
Barnsley looked the more likely winners after this but had to settle for a point.
BARNSLEY LINE-UP: Scarsella, Austin, Williams, Laight, Atkinson, Heslop, Burns (off 45), Tonge, Stallard, Onibuje (Scothern 86), Baker.
SHEFFIELD UNITED LINE-UP: Barnes, Francis (Roma 73), Horwood, Montgomery, Robertson, McFadzean (off 57), Hurst, Ross, Lester (Marrison 64), Sharp, Forte (Harper 73).