Having lost four of their last five matches, Charlton had slipped out of the top six but Birmingham's home defeat by Leicester and the Addicks' win took them into a Champions League position as they bid for their highest ever Premiership finish.
It took a goal of sublime quality from their skipper Matt Holland to take the three points and dramatically improve their home record which was inferior to their away form in their bid for a European place.
Middlesbrough had played three matches in the last two weeks while Charlton, without a game last weekend, had been able to plan and rest for the game.
The visitors were punished for getting off to a slow start although they could have taken the lead in the eighth minute when Boudewijn Zenden hit the inside of the Charlton post only to see the ball rebound back into play.
Charlton took the lead in the 26th minute with a goal out of the blue which was worthy of winning any game.
Holland played the ball to Paolo di Canio who returned it into the path of the Charlton skipper. He looked up and from 25 yards sent in a curling chipped shot into the top corner of the net past the helpless Mark Schwarzer.
Middlesbrough had another chance to level just before half time when Juninho shot from close range straight at Charlton goalkeeper Dean Kiely.
Boro boss Steve McClaren made two substitutions at the start of the second half, bringing on Massimo Maccarone and Szilard Nemeth, as he decided to play with three strikers in an attempt to get back into the game.
For a period they dominated although Charlton went close to increasing their lead when Claus Jensen's free-kick went just over the bar.
Charlton brought on striker Shaun Bartlett for Carlton Cole and the home substitute hit the outside of the post as he got clear of the Middlesbrough defence.
Charlton were pushed back and were unable to get out of their own half for a spell as Boro piled on the pressure.
Kiely made a couple of crucial saves to keep his side in front, stopping an effort from Nemeth and in stoppage-time saving from Maccarone with his legs.
But the home side held on for a victory that could prove vital at the end of the season.
Charlton boss Alan Curbishley was delighted with the result in view of his team's recent results and the fact that they had been disrupted through injury and were without a number of players for this match, including the influential Jason Euell.
"If you look at the stats it was probably quite an even game," he said.
"They threw caution to the wind in the second half and we got hemmed in and lost our composure.
"We haven't won enough games here and the players want to put that right. They are an honest bunch of lads and they saw the importance of this victory.
"I was delighted with the goalkeeper and especially with the back four who got their bodies in the way of the ball when it mattered."Charlton are now beginning to get up a head of steam at home after some disappointing earlier results and have now won four of their last six matches at The Valley.
Their remaining fixtures are against sides who they will be hoping to pick points up from, while away they have yet to play three or four of the top sides so it is vital that they keep their home form on track.
Boro boss McClaren took a more rose-tinted view of the match, claiming he would have been disappointed if his side had only drawn.
"We looked a very good team today and will play much worse than this and win," he said.
"It was one of those days which you can't explain. I thought we dominated the match and could have scored two or three goals, but I can't fault the players for their performance and we played some great football although the end product wasn't there.
"Their keeper kept them in the game and I am baffled as to how we failed to get anything out of the match."With £500,000 at stake for each position in the Premiership, McClaren is desperate to get his side up the table.
Having already qualified for Europe as a result of winning the Carling Cup, Boro are now looking to get as many wins as they can in the remaining games of the season.
Their form this season has been somewhat inconsistent and like a number of teams they have often looked better away from home than on their own ground.
This was evident with some of their play in this match but they lacked a cutting edge and had they been more ambitious in the opening 45 minutes they may well have come away with something out of the game.
Young Charlton striker Cole, who is on loan from Chelsea, stormed to the dressing room after being substituted on 59 minutes but later sheepishly returned to sit in the dug-out.
Curbishley passed the incident off saying: "Carlton is a young lad of 19 and this is just part of the learning curve that he is going through. He didn't need telling he shouldn't have done it and he realised that but it is no big deal."Man of the Match: Charlton - Danish international midfielder Claus Jensen dominated in midfield, working tirelessly from defence to attack along with his central midfield partner Matt Holland to keep Charlton going when it got tough.