Early in the second half at Selhurst Park goals from Robert Huth and Jamie Vardy had taken the visitors close to a momentum-building victory just four days ahead of their Champions League quarter-final second leg with Atletico Madrid.
Palace then swiftly responded through Yohan Cabaye and Christian Benteke then secured the draw that took them up to 15th, seven points clear of the bottom three and within five of ninth.
Palace XI: Hennessey, Ward, Kelly, Sakho, Schlupp, Milivojevic, Cabaye, Townsend, Puncheon, Zaha, Benteke
Subs: Speroni, Van Aanholt, Flamini, Campbell, McArthur, Sako, Delaney
Leicester: Schmeichel, Simpson, Benalouane, Huth, Fuchs, Mahrez, Ndidi, King, Albrighton, Vardy, Ulloa
Subs: Chilwell, Drinkwater, Musa, Amartey, Okazaki, Zieler, Gray
Referee: Mike Dean
WHAT THEY SAID
Sam Allardyce: "We have given ourselves a little cushion above the bottom three. We have won five out of six but I have told my players not to lose focus.
"It'll be an interesting challenge for us to see if we can take on Leicester, master their tactics and be clever enough to beat them.
"You'd expect one or two changes for them, but they've got a very good squad. They'll be tough to beat, back to their old selves."
Craig Shakespeare: "Having worked with Sam in a very short space of time his record there is for all to see. He's never been relegated from the Premier League.
"Having seen him work at close quarters, how diligent he is on the opposition it doesn't surprise me."