The hosts dominated from start to finish but were denied three points by a combination of poor finishing and a string of fine saves from Barnsley stopper Luke Steele.
United, with just one win from seven, almost found a way through in the opening minutes, Richard Cresswell picking out Jamie Ward, but the diminutive striker stumbled when well-placed.
The Barnsley keeper pulled off a stunning save minutes later from Richard Cresswell's header.
Glen Little's teasing header landed perfectly for Cresswell but Steele was equal to the test.
Ward saw his close range strike charged down by Steele before he limped off in the 34th minute with a hamstring injury that could keep him out for the rest of the campaign.
Barnsley, weakened by the absence of injured striker Daniel Bogdanovic, struggled to break down the United defence with Chris Morgan facing Iain Hume for the first time since his clumsy challenge left the Canadian with a fractured skull in November 2008.
Hugo Colace's free-kick tested Blades keeper Steve Simonsen and at the other end substitute Mark Yeates tried his luck with a long-range strike but his effort sailed high over the target as the home side grabbed a stranglehold on the game.
Little dragged the ball wide from inside the area and Luke Potter almost sliced the ball into his own net.
In the dying minutes, Steele pulled off another spectacular stop to keep out Darius Henderson's goal-bound header.
There was further misery for United as defender Paul Connolly was dismissed with seconds to go for a second bookable offence.