A 3-1 home defeat by Southampton on Friday left Palace in the relegation zone, third from bottom on 15 points from 18 games. Warnock, appointed in August, is the first Premier League manager to lose his job this season.
"Crystal Palace Football Club can today confirm that Neil Warnock has been relieved of his duties and is no longer first-team manager," Palace said on their website (www.cpfc.co.uk).
"The club would like to put on record its thanks to Neil for all his hard work and energy over the past four months."
The London club have lost three and drawn three of their last six games, their last win coming against Liverpool on Nov. 23. Palace make the trip across London to face Queens Park Rangers on Sunday with Keith Millen taking charge as caretaker manager.
Warnock, 66, returned to Selhurst Park after Tony Pulis, who had steered them to an 11th-place finish against the odds last season, departed two days before the start of the current campaign.
Warnock left Palace in 2010 after they went into administration, joining Queens Park Rangers and taking them into the Premier League before being sacked eight months later, in January 2012.
The following month he was appointed manager of Leeds United, only to be fired just over a year later.
Warnock has managed 13 clubs, starting in non-League football almost 35 years ago.
(Reporting by Justin Palmer; editing by Ed Osmond)
