Jonathan Stead scored a priceless equaliser for Sheffield United which keeps Charlton in the bottom three.
Stead gave Sheffield United's survival chances a huge boost
Talal El Karkouri put Charlton ahead after 59 minutes when his 35-yard shot took two deflections and crept in.
But 10 minutes later, Stead levelled matters with a sweetly-struck goal from the edge of the area.
Charlton threatened a winner when Zheng Zhi volleyed wide but the Blades deservedly held on for the point which boosts their survival hopes.
The match between the two relegation rivals was billed as the "£30m game" and Charlton gave it an appropriately dramatic build-up.
Abba tribute band Bjorn Again provided the music as Addicks icon Derek 'Killer' Hales urged the home crowd to be the team's 12th man.
But the visitors came close to putting a dampener on the atmosphere inside two minutes.
Keith Gillespie swung over a dangerous low cross which was just too far in front of Lucas Shelton - who was booked for using his hand to try to guide the ball home.
However, Alan Pardew's decision to field a side full of attacking intent, with Jerome Thomas and Dennis Rommedahl supporting Darren Bent up front, soon began to pay dividends.
Rommedahl, in particular, looked threatening down the right and from his cross, Darren Ambrose headed just wide.
Bent, who passed a late fitness test on his calf injury, lost his marker but volleyed wide from Ambrose's corner before Paddy Kenny tipped over El Karkouri's deflected free-kick.
Blades boss Neil Warnock responded to Charlton's early pressure by switching Chris Armstrong to left-back to deal with Rommedahl, moving Matthew Kilgallon into the centre and Phil Jagielka into midfield.
Pardew could only look on in frustration as Charlton toiled
That allowed his side to gain a foothold in the game and after 33 minutes, Scott Carson did well to tip Gillespie's header round the post from Armstrong's deep left-wing cross.
But as the minutes ticked by, the tension hanging in the air began to stifle the game.
With 10 minutes of the second half gone, Pardew began to think about making changes, sending substitute Jimmy Floyd Hasselbaink to warm up.
But Hasselbaink was soon sitting down again as El Karkouri's speculative 35-yard shot came off Michael Tonge and then Kilgallon before creeping under Kenny's outstretched hand.
Fortunate though it was, the goal failed to settle Charlton's nerves.
They gave away a succession of free-kicks to allow the opposition to dominate and it was little surprise when the Blades equalised.
Montgomery slipped the ball through to Stead on the right-hand edge of the area and the former Blackburn striker powered it into the far corner.
That was the cue for Hasselbaink to make his entrance, but Charlton continued to toil.
The Blades' defence faltered just once when they allowed Zheng a free volley but the Chinese midfielder missed from six yards.
Defeat would have been harsh on the Blades, who remain two points clear of 18th-placed Charlton with three games to go.
Sheffield United boss Neil Warnock:
"I think you could see we came to try to win the game and I thought we played some good stuff at times.
"Charlton's opener was disappointing but my lads fought back really well and it was fabulous strike by Jon Stead. I think we deserved it.
"A lot of people didn't think we'd be where we are but we're right in amongst it, fighting for our lives."
Charlton boss Alan Pardew:
"It was a tight, tense affair. Both sets of players carried the burden of trying to stay in the Premiership.
"I was happy with the way we played, but our goal actually affected us in a negative way more than it did them. We had our worst spell after we scored.
"But we're still right in there, so we fight on."
Charlton: Carson, Young, El Karkouri, Diawara (Bougherra 76), Thatcher (Hreidarsson 71), Zheng, Song Billong, Ambrose, Rommedahl, Darren Bent, Thomas (Hasselbaink 73).
Subs Not Used: Randolph, Holland.
Booked: Song Billong, Diawara, Zheng, El Karkouri, Hreidarsson.
Goals: El Karkouri 59.
Sheff Utd: Kenny, Geary (Leigertwood 83), Morgan, Jagielka, Kilgallon, Gillespie, Tonge, Montgomery, Armstrong, Shelton (Kazim-Richards 60), Stead.
Subs Not Used: Bennett, Kozluk, Nade.
Booked: Shelton, Montgomery, Kenny.
Goals: Stead 69.
Ref: A Wiley (Staffordshire).