The Eagles parted company with Tony Pulis last week following claims that the Welshman was unhappy with the club's transfer policy.
Keith Millen was installed as caretaker manager for the defeat to Arsenal on Saturday, but co-chairman Steve Parish made it clear that he was looking to make a swift appointment.
Mackay arrives at Selhurst Park having been sacked by Cardiff last December, with the Bluebirds lying in 16th in the Premier League and just one point above the relegation zone.
It's thought that he will be in charge for Saturday's match against West Ham after beating Tim Sherwood to the Palace hotseat.
I'm sure once Mackay is appointed, the Gilet wearing rent a gob moron Sherwood will let the media know that it was actually he who turned down Palace as the club didnt match his ambition and was not the right fit for him. I'm sure after two years of unemployment he will finally find his level in league 2.- bigo