The 24-year-old made a return to the venue where he played for many years, as Palace continued their resurgence in the campaign.
Christian Benteke opened the scoring by 18th minute before Wilfried Zaha added another goal on 40th minute with a fine finish.
Great result against a strong team! Fans were amazing as always!Also nice to be back at the KP stadium and getting such a great reception 💙 pic.twitter.com/MjLTFPkfUc— Jeffrey Schlupp (@Jeffrey_Schlupp) December 16, 2017
Leicester's Onyinye Ndidi was sent off after picking his second booking of the day by the 61st minute, before Schlupp also saw a yellow six minutes later.
While the hosts searched for a late consolation, Bakary Sako made it 3-0 on the stroke of full time as Palace moved further up on the log.
“Great result against a strong team! Fans were amazing as always!Also nice to be back at the KP stadium and getting such a great reception,” Schlupp wrote on Twitter.
The Eagles lost their opening four games without scoring a goal and became the only club aside Preston North End to suffer same faith during the 1924-25 season but they have now gone six games without a defeat and sit 14th on the log with 17 points, two points above the drop zone.
Ghana defender Daniel Amartey was once again out of Leicester's matchday squad, stretching his idleness to almost six weeks.