Goals in each half from Joel Ward and Wilfried Zaha were enough to secure a win against out-of-form opposition, whose only response came from Oriol Romeu.
When Alan Pardew was appointed Palace manager, a little over 12 months ago, his priority was to retain their Premier League status when they were at threat of relegation.
His move there came after a largely miserable four years at Newcastle, where part of the consistent criticism he received from the club's fans was at a perceived lack of effort made to win competitions such as the FA Cup
Pardew has since frequently spoken of the satisfaction he has taken with the greater authority he enjoys at Palace - it is no secret Newcastle's hierarchy discouraged the pursuit of silverware when their ambition was to remain in the Premier League - and with his team thriving and depth in his squad, he now has little excuse but to take it seriously.
To that end, he has spoken of the competition becoming a priority, and while there were rare starts for Joe Ledley and Jordon Mutch, Pardew recalled Yohan Cabaye in the hope of ending a run of three games without a goal.
The situation for Southampton, one of Pardew's former clubs, is rather more serious
At risk of joining the battle against relegation to the Championship, manager Ronald Koeman could be forgiven for considering this fixture a further distraction, but despite recalling Sadio Mane and starting Romeu, Matt Targett and Maya Yoshida, his team was also near full-strength.
Shane Long has impressed for Southampton in recent weeks, and in the opening period he again threatened by dragging Wayne Hennessey out of position before watching the goalkeeper impressively recover to save his close-range shot.
It was Palace, however, largely inspired by former Southampton forward Jason Puncheon, who scored the opening goal in the 29th minute
Puncheon dispossessed former team-mate Steven Davis in central midfield, dribbled from around the halfway line into the hosts' penalty area and squared to give Ward a routine finish from directly in front of goal
Southampton's already-low confidence clearly began to further deteriorate, and Koeman unsurprisingly responded at half-time by introducing Dusan Tadic and Juanmi for Yoshida and Davis, reverting from a back five to a four.
Their response was almost instant
When Mane tested Hennessey with a 51st-minute shot, Romeu reacted to the rebound, and from close range produced a routine finish to score the equaliser
Playing with greater belief, the hosts appeared the more likely victors, until in the 68th minute Palace again took the lead and in doing so sealed victory.
Goalkeeper Maarten Stekelenburg could only parry Puncheon's shot to the lively Zaha, and from the centre of the area the talented forward sent a powerful shot into the back of the net.
Again, Southampton's heads dropped
This time, however, a substitution did not change the game, and late on Jose Fonte heading against the crossbar, and Virgil van Dijk heading against the post, were the closest they came to avoiding a third successive defeat.
Source : PA