Goals from skipper Johnnie Jackson and striker Danny Haynes cancelled out a first-half strike from Danny Swanson, before Michael Bostwick equalised 19 minutes from time.
After two disappointing home defeats to Nottingham Forest and Burnley, The Addicks were desperate to turn their fortunes around and avoid being dragged into a late relegation battle.
Chris Powell made three changes to the team that lost 1-0 against Burnley on Saturday. Fan's favourite Chris Solly was back after missing through injury, Matt Taylor came in for the injured Leon Cort and there was a first competitive start for Callum Harriott who came in for Jon Obika.
The Addicks started the better and came close to scoring just 4 minutes in. Shouts of handball chorused from the home crowd when they argued a clearance had been blocked by Lawrie Wilson's hand. Play went on and Charlton's versatile right-sided player hit a curling left-footed effort that bounced off the underside of the crossbar, then out.
Charlton then went close again when Ricardo Fuller - searching for his first goal in over a month - hit a shot just wide of Robert Olejnik's goal.
The former Jamaican international then turned provider by heading on to Danny Haynes who hit a half-volley straight into Olejnik's arms.
The visitors continued to dominated and after a good passing move, Wilson crossed for Fuller in the box, but the forward could on direct the ball into the keeper's hands.
Peterborough created their first real chance shortly after. Mark Little crossed from the right to Mendez-Laing at the back post, but David Button was quick and managed to smother the ball from the feet of the attacker.
Michael Morrison was then the hero for Charlton. Mendez-Laing smashed the ball across Button, but the Charlton defender was there to clear off the line.
Defender Gabriel Zakuani then lashed the ball over from 6 yards after Charlton failed to deal with a corner.
Peterborough's confidence was growing and they finally snatched the lead on the 28th minute. Morrison failed to clear his lines, allowing Danny Swanson to run through on goal and slot past Button for 1-0.
The home side continued to dominate and almost scored again shortly before half-time. Mendez-laing was played through brilliantly, but Button got down well to only concede a corner one-on-one.
After the half-time team talks, Peterborough almost scored seconds after the restart. The Charlton defence opened up and Lee Tomlin struck the outside of the post.
Charlton knew they had to up their game if they were to avoid a 3rd straight defeat. Callum Harriott went close when he hit a half-volley 20 yards out just wide of the post.
Harriott was heavily involved in Charlton's next opportunity, as The Addicks got a vital equaliser. The youngster threaded the ball through to Jackson who took a touch, then delicately placed the ball beyond Olejnik for 1-1.
The captain's name was sung repeatedly by the hardy Charlton fans behind the goal he had scored in. Four minutes, they were given even more reason to be jubilant.
After a Charlton corner wasn't dealt with, the ball came out to Solly on the right who crossed for Morrison at the back sticks. The defender's header was saved by a mixture of keeper and defender on the line, but the rebound fell out to Haynes who rifled his shot high into the net to turn the game on it's head.
Charlton were starting to show the form that has got them 7 away wins already this season and should have scored a 3rd minutes after their 2nd.
Haynes was through one-on-one and with the keeper opting to commit himself, the striker chose to pick out Fuller at the far post, but Zakuani headed away to safety.
Haynes went close again, but could only loop his header over the bar from Jackson's left-footed cross.
Charlton had their skipper to thank for keeping them infront up the other end. Jackson put his full body on the line to block a certain goal from the home side.
However, on the 71st minute, The Addicks let slip a lead for the 9th time this season. Michael Bostwick was given the freedom of the midfield and shot from outside the area beyond Button who will definitely feel he could have done better.
Charlton did have a couple of opportunities to take the lead again. Jackson had a free-kick 20 yards out that was tipped over the bar by Olejnik.
Jackson then set-up Haynes from a corner that was headed wide of the target.
Powell then brought on Obika for Fuller. The Spurs loanee was denied by a fantastic block 6 yards out from Bostwick.
Time was running out and in the 4 minutes added on at the end, Dorian Dervite was brought on to show the Charlton Boss was content with a point.
There was still time for one last Peterborough attack. A corner was met by Dwight Gayle who was denied by Button and then Jackson superbly cleared off the line to keep hold of a valuable point.
The match was over and Charlton had over-taken Millwall in 14th place on goal difference. Peterborough drop to 23rd and have to continue the fight in beating the drop.
The Addicks now travel to Huddersfield on Saturday hoping to get closer to the 50-point mark. Peterborough host Ipswich in a vital 6-pointer
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