Palace notched their fifth consecutive home win as Terry Venables put one over his old club Portsmouth.
Australian international Craig Moore opening the scoring for the Eagles after only six minutes, his third in five games since his £800,000 move from Glasgow Rangers last month.
Fellow Australian Nicky Rizzo's in-swinging corner was met superbly by Moore who headed powerfully past Alan Knight in the Pompey goal.
Matt Jansen and Sun Jihai missed good chances to increase Palace's lead, and at the other end, Steve Claridge did likewise for Portsmouth.
About four minutes before the break, just as Portsmouth were battling hard to get back into the game, Fitzroy Simpson was given his marching orders by Midlands referee Paul Rejer after elbowing Dean Austin near the right touchline.
But within seconds 10-man Pompey were level. Fan Zhiyi failed to clear in his goalmouth, and John Aloisi pounced from a few yards out to bag his 15th goal of the season.
After the break, Palace took control. On 57 minutes, Jansen wiggled his way into the box, and although his left-foot shot was wayward, the ball struck the unlucky boot of Andy Thomson and whistled past the helpless Knight.
Seven minutes later, Palace increased their lead further after Rizzo cleverly back-heeled to Hayden Mullins who from 10 yards out swept the ball under Knight.
Attilio Lombardo hit the post, and Knight pulled off several brilliant saves before Craig Foster scored Palace's fourth from 20 yards out, his first goal since his move to Palace last month.
Substitute Marcus Bent hit the post, and Knight again pulled off more saves to avoid an embarrassing scoreline.