The victory enhanced Blackburn's hopes of European football next season.
The Charlton boss, who has been embroiled in the saga of the England managerial appointment, is to quit the club after next week's final game away at Manchester United.
His departure was surprisingly announced on the pitch before the match - strange timing - by chairman Richard Murray and Curbishley was applauded out onto the field by both teams and supporters.
It left a strangely muted atmosphere for his players to lift themselves to get a result for him, but sadly they were unable to raise their game and it was no surprise when they fell behind a minute before half-time to a poorly conceded goal.
Morten Gamst Pedersen's long throw was missed by Gonzalo Sorondo and with goalkeeper Stephan Andersen, playing his first Premiership game since November, stranded on his line Steven Reid had the simple task of heading home from close range.
Darren Ambrose had a couple of good chances to score for the home side but sent both his efforts straight at goalkeeper Brad Friedel.
Charlton showed little threat and Curbishley threw on striker Kevin Lisbie, recalled from a loan spell at Derby County, and young winger Lloyd Sam, who has been out of action for most of the season.
The home side were unable to raise their display and Blackburn were happy to take advantage when gifted a comical second goal.
Florent Sinama Pongolle's harmless cross was missed by Andersen and deflected into the net by defender Chris Powell under pressure from the lively Craig Bellamy.
It was a disappointing end for Curbishley, but typical of Charlton's usual end of season slump.
Despite the fact that Charlton have maintained their Premiership status for another season Curbishley obviously feels he has taken the club as far as he can.
He hasn't managed to take them the next step into Europe and they were beaten in the quarter-finals of the FA Cup by Middlesbrough, and always seem to stutter at the crucial point.
Although he still has a year on his current contract to run, Curbishley was unsettled by the England saga and decided to go after a lengthy meeting with the chairman on Friday.
With the possibility of Curbishley getting the England job the Charlton board were already looking at alternatives.
Those options will obviously come into play now and Reading boss Steve Coppell is the early favourite to replace him, although there will no doubt be many others who will come forward.