Defoe scored in the 80th minute of the Premier League encounter at Selhurst Park.
It proved to be the only goal of the match, as Sunderland picked up three valuable points in their attempt to avoid relegation to the Championship at the end of the season.
The 33-year-old has admitted that he got lucky with his goal, but he has insisted that the win is a result of the hard work the players put in during the two-week international break.
"The lads worked hard,” BBC Sport quotes Defoe as saying. “We put the work in during the international break and it paid off.
"I got that little bit of luck that you need for the goal and I was just delighted. The manager has been fantastic. He has got the lads working hard.”
Over the course of the 90 minutes at Selhurst Park, Palace had 67% of the possession, took 19 shots of which seven were on target, and earned 11 corners.
Visitors Sunderland had 33% of the possession, took 12 shots of which just four were on target, and earned two corners.
The Black Cats are third from bottom in the Premier League table at the moment with nine points from 13 matches, just a point behind 17th-place Newcastle United.