Marcus Tudgay snatched a last-minute winner to help Barnsley overcome 10-man Millwall at The Den this afternoon.
The hosts should have taken the lead on 27 minutes, after Darius Henderson had been brought down in the penalty area by Scott Wiseman.
However, Henderson took the spot kick himself and blazed it high and wide.
Stephen Dawson punished that error four minutes later, tapping home from close range after Chris Dagnall had been denied by David Forde.
Millwall's difficult task was made even harder nine minutes into the second period when Adam Smith was shown a straight red card for a two-footed tackle on David Perkins.
However, the Lions coped well with their numerical disadvantage and, with 10 minutes remaining, Chris Wood levelled the scores with a well-taken finish from close range.
Barnsley went back ahead in stoppage time, though, when Bobby Hassell found Tudgay, who found the net from from 12 yards.
The Tykes move up to 22nd place in the Championship table and are now only in the relegation zone by virtue of goal difference.
