Ross McCormack’s goal 12 minutes from time gave the Villans all three points as they move into the play-off picture under Steve Bruce.
Leandro Bacuna’s early goal was cancelled out by Jamie Ward, but summer signing McCormack tucked home Jordan Ayew’s cross at the far post to seal the win.
Sam Winnall’s tenth goal of the season gave the Tykes victory at Oakwell.
The striker headed home after 14 minutes to put the hosts ahead, before goalkeeper Adam Davies kept them in front with a superb save to deny Wes Brown.
Blackburn, though, seemed unable to get a foothold into the game allowing Barnsley to see the match out on home soil.