Paolo Di Canio's side looked on course to pick up all three points thanks to Emanuele Giaccherini's first-half goal but Mauricio Pochettino's men snatched an equaliser late on
Emanuele Giaccherini gave the visitors an early lead but Southampton dominated proceedings and saw a Jay Rodriguez goal ruled out for offside and two penalty appeals turned down as they struggled to find a breakthrough.
However, after Rickie Lambert had scored a 90th-minute winner against West Brom last Saturday, Jose Fonte popped up with a last-gasp header to equalise two minutes from time.
|VIEW FROM ST MARY'S STADIUM
|By Liam Twomey
The dominant feeling as Southampton fans streamed out of St Mary's at full time was one of relief, but a draw that feels like a win is still a draw. Mauricio Pochettino's men made the running throughout, but their efforts were hamstrung by some slack marking from a corner on three minutes which allowed Emanuele Giaccherini to head in his first goal in English football.
At times only Kieran Westwood stood between the Saints and a comfortable victory, but more often the likes of Rickie Lambert and James Rodriguez were their own worst enemies with some uncharacteristically poor finishing. Daniel Osvaldo showed flashes of promise during his second-half cameo, without threatening the goal himself.
In the end Jose Fonte rode to the rescue and, judging on their performances so far, Southampton cen be confident of enjoying a good season. For Sunderland and their combustible boss Paolo Di Canio a solid foundation is evident, but that dysfunctional attack remains a big worry.
Mauricio Pochettino was able to name an unchanged starting line-up from the victory at the Hawthorns, while new signing Pablo Daniel Osvaldo began on the bench.
Meanwhile, Craig Gardner returned to the Sunderland fold after completing a three-match suspension, but Wes Brown remained sidelined with a knee injury.
Paolo Di Canio's new-look side wasted a number of good chances during their narrow opening-day defeat to Fulham last weekend but looked keen to make amends as they took their first opportunity at St Mary's.
Giaccherini headed home from a brilliant Sebastian Larsson corner inside three minutes to claim his first goal for the club.
Southampton thought they had grabbed an immediate equaliser when Jay Rodriguez picked up a throughball from Lambert and slotted past Keiren Westwood, but their celebrations were cut short as the forward was ruled offside.
There was a flurry of chances after the early drama and Lambert almost pulled Southampton level in the 18th minute as he met a cross from James Ward-Prowse with a powerful header, but Westwood got down well to turn the ball around the post.
Southampton claimed for a penalty in the 36th minute as Fonte went to ground in the area, but referee Lee Mason was not interested.
There were more boos for the referee just before half-time as Adam Lallana seemed to be hauled down by John O'Shea, but the hosts' appeals fell on deaf ears.
Pochettino brought on Osvaldo for the second half in an attempt to find an equaliser and the Italy international immediately gave Southampton more confidence in the final third as he set up Lallana, but the midfielder fired just wide.
Osvlado then clipped a brilliant ball into the six-yard box for Rodriguez in the 58th minute, but the striker headed straight at Westwood.
Southampton continued to threaten the Sunderland goal but Lambert could not find a way past Westwood - the goalkeeper palming away his powerful 20-yard shot before keeping out a header at the far post.
The hosts saw another penalty appeal rejected by the referee during the closing stages when O'Shea climbed on Osvaldo in the box.
But it did not matter as Fonte headed home from a deep Ward-Prowse free kick in the 88th minute to grab a deserved equaliser and point for Southampton.