Blackpool's play-off hopes took a dent when they slumped to their first home League defeat since November 9.
Barnsley survived an early Seasiders onslaught with keeper Andy Marriott denying Martin Bullock on three minutes and then producing a double save to rob Richard Walker of a goal on 22 minutes.
Tykes striker Mike Sheron had revealed his liking for Blackpool's defence when he scored two against them at Oakwell earlier in the season and he should have scored with a 25th minute header from five yards out but made no mistake in the 42nd minute when Mitch Ward him Sheron lurking in the box.
The pacy ex-Manchester City striker turned inside Colin Hendry and gave Phil Barnes no chance with a good angled drive.
This shook Blackpool who were finding it difficult to wear down the Tykes defence which had Walker and fellow striker John Murphy well in check.
However, after the break Blackpool once again applied themselves and Murphy grabbed his 18th of the season in the 55th minute.
For once the big striker was not involved in an aerial battle and with the ball played to his feet by Simon Grayson Murphy turned well and beat Marriott with a low shot from 15 yards.
Barnsley were not shaken and immediately hit back.
Seven minutes after the equaliser Sheron was once again on target. He punished some lax marking on the edge of the penalty area and once again had time to turn and shoot past Barnes.
The introduction of Ritchie Wellens sparked a late flurry of home attacks but the Barnsley defence proved resolute and managed to see out six minutes of added time.
Afterwards Barnsley assistant manager Colin Walker said: "We are beginning to put together a really decent run.
"We are beginning to know how to win games and our confidence is rising.
"We took everything they could throw at us and even when Blackpool equalised we came straight back and grabbed the winner. It was a terrific team performance." Disappointed Blackpool boss Steve McMahon said: "We knocked on the door a lot but really that was it. We put them under the cosh but bar Murphy's goal there were long periods in which we didn't create any clear cut chances.
"If we had play off credentials it should have been a three point home win."