Henning Berg was sacked as manager on Thursday following one win in 10 games at the helm.
Rovers' senior coaching staff were also shown the door and, under the caretaker control of reserve-team boss Gary Bowyer, it was the only signing of Berg's 57-day reign that opened the scoring at Oakwell.
On-loan Manchester United forward Josh King bundled home before the half hour and a sublime individual effort on the stroke of half-time from Ruben Rochina gave Blackburn breathing space.
Stephen Dawson reduced the arrears during a lacklustre second half, the closing stages of which were marred by the sight of Barnsley forward Marcus Tudgay receiving lengthy treatment following a collision with Rovers goalkeeper Jake Kean and leaving the field on a stretcher.
That reduced Keith Hill's side to 10 men having used all their substitutions and, in the eighth of nine additional minutes, Jordan Rhodes muscled his way on to Jason Lowe's long ball to seal Blackburn's triumph and send Barnsley to the foot of the table.
Barnsley almost took the lead in the ninth minute when Scott Dann's botched clearance presented Craig Davies with an opportunity but Rovers managed to scramble clear.
Davies had the ball in the net with 17 minutes played but the whistle had gone for a foul on Adam Henley and Blackburn then began to make most of the running.
Blackburn opened the scoring when straight from a Kean clearance, King raced clear of the Tykes backline and, although Luke Steele saved his initial effort, the rebound struck him and bobbled into the net.
Rovers remained on the front foot and were rewarded in style by Rochina.
Wiseman backed off the advancing former Barcelona B playmaker, who stormed into the penalty area and lashed past Steele at his near post.
Sub Colin Kazim-Richards almost extended Blackburn's lead in the 54th minute, seeing a shot deflected behind. That opportunity was inventively set-up by Rochina and Blackburn let the initiative slip after he limped off midway through the half.
Barnsley sensed the opportunity and, with 14 minutes to go, Dawson lashed home emphatically from 20 yards. The host's charge for an equaliser was concluded without Tudgay - leading to the huge allocation of injury time that Rhodes crowned with his 12th Blackburn goal in 21 starts.