Barnsley 3 Hull City 0
A goal apiece from Istvan Ferenczi and Peter Rajczi sealed the points for the home side despite a late rally from Phil Brown's battlers.
Ferenczi, 29, a January £250,000 buy, along with his countryman, marked his first home start with a cool finish after his consolation goal in Barnsley's 5-2 defeat at Southampton on Saturday.
A long clearance from home keeper Nick Colgan had the Hull defence in a flap, Michael Turner failed to clear and Ferenczi snapped up the loose ball and slotted his shot past Boaz Myhill.
Ex-England and Arsenal star Ray Parlour, in his first start for Hull, showed his style and class and produced a string of clever passes but striker Nicky Forster saw a shot blocked after being sent in by Parlour.
Parlour, signed on a short-term deal after being released by Middlesbrough, relished his roving role in the centre of midfield and was at the heart of Hull's positive moves.
And when Forster cut inside from the right he scooped an ambitious long-range effort high over the bar. But Barnsley came close to claiming a second goal with an audacious free-kick routine.
Brian Howard and Grant McCann were involved in the cleverly choreographed routine before Martin Devaney spun smartly but finally failed to trouble Myhill with a tame shot.
But the home side stretched their lead 30 seconds into the second half with a superbly taken goal from 25-year-old Rajczi.
Ferenczi challenged for the ball and it broke for his countryman who ran 30 yards before firing his shot past Myhill.
Hull produced a spirited second-half reply and Paul Heckingbottom had to head off the line after Hull went close soon after the second goal.
But Barnsley were not to be denied and rounded off the victory when Ferenczi snapped up the third goal after 76 minutes when he charged into the area and headed in a pinpoint cross from Howard.