It was a crucial point for Saints as it lifts them four points clear of the relegation zone.
After a quiet first half which saw Pierre-Emile Hojbjerg have a shot saved by Palace goalkeeper Vicente Guaita, the visitors took the lead four minutes before the interval.
Andros Townsend was brought down on the edge of the penalty area but the referee waved play on and Wilfried Zaha was on hand to smash his shot into the bottom corner of the net.
The goal rocked Saints and they were unable to respond before the interval although, immediately after the break, Guaita kept Danny Ings’ effort out.
Palace thought they had doubled their lead when Mamadou Sakho poked the ball into the net but the referee ruled that Jordan Ayew had fouled Alex McCarthy in the build-up.
After Townsend had lashed a shot over the bar, Southampton equalised with 14 minutes left when Ward-Prowse drilled a shot home after being set up by Matt Targett.
The home team pressed for a late winner and Stuart Armstrong was denied by Guaita while Zaha was sent off in the closing moments. The Palace star was booked for his challenge on Ward-Prowse and, when he gave the referee a sarcastic clap, was handed a second yellow card for dissent.