Former Addicks boss Pardew looked set for victory when Adam Lallana put Southampton ahead but Deon Burton's fourth goal of the season earned the hosts a share of the spoils.
Burton and Jonjo Shelvey also had efforts disallowed for offside, while Lloyd Sam appeared to be tugged down in the penalty area late on by Dan Harding.
Pardew, who was barracked by the home support throughout, said: "The crowd's reaction was understandable given that I wasn't a success when I was here.
"We bossed the first half and I thought we were going to get a second goal when we came out for the second half. Unfortunately, we made a silly error for their goal and we went on the back foot a bit. It wasn't until 10 minutes from the end that we got back in it but we've improved considerably and we just need that win now."