The Addicks took the lead with just eight minutes left, but Barnsley snatched a last-minute equaliser to keep up their recent good form and take their own unbeaten run to six matches.
In an excellent open and attacking match, Charlton had the better of the chances until the latter stages of the game and, after snatching their late equaliser, Barnsley could have taken all three points when Grant McCann fired wide with only the goalkeeper to beat, deep into injury time.
Charlton twice hit the bar, the first time as early as the ninth minute through skipper Andy Reid and Chinese midfield player Zhi Zheng also headed against the woodwork for the home side in the second half.
Charlton kept up their record of scoring in every match this season, when their second-half pressure brought them a deserved lead on 82 minutes.
Reid's cross was headed on by Chris Iwelumo for Zheng to plant his header firmly wide of Heinz Muller in the visitors goal.
It should have been enough to give Charlton victory but Barnsley's two late substitutes contrived to snatch a point for the Yorkshire team when Martin Devaney's cross fell for Kim Christensen to score from close range.
Then came that let-off for Charlton when McCann missed his last-gasp chance but it would have been a travesty of justice had the Addicks been beaten.
Both the sides had been in excellent form recently and with ten matches gone Charlton have been beaten only once and are still in the second automatic promotion place while Barnsley have been one of the surprise sides of the season.
Charlton's early chances after Reid's effort which hit the bar fell to Zheng who headed over but Charlton keeper Nicky Weaver had to be alert to save an effort from former Charlton player Jamal Campbell-Ryce just before half-time.
After the interval Charlton replaced Luke Varney with Svetoslav Todorov and they took control of the game but Barnsley defended well although Darren Ambrose missed a sitter for the home side firing wide of an open goal.
Before Zheng opened the scoring for Charlton, Reid saw his free-kick saved and Madjid Bougherra had had his header cleared off the line.
This was a good advert for the Championship but Charlton boss Alan Pardew will be disappointed that once again his team conceded a late goal.