The supernatural drama will star Terry O'Quinn (Lost) and Vanessa Williams (Desperate Housewives) as the owners of a haunted building.
Palladino guest-starred in the show's pilot, but has now been made a main cast member, Deadline reports.
The 44-year-old actor plays Tony DeMeo, the doorman at the haunted residence The Drake
Palladino has previously starred on ER, Joan of Arcadia, Criminal Minds and Make It or Break It.
666 Park Avenue - which also stars Dave Annable (Brothers & Sisters) and Rachael Taylor (Charlie's Angels) - was recently voted the most exciting new ABC show by Digital Spy readers.
> Vanessa Williams on 666 Park Avenue: 'I play a seductive role'
Watch the trailer for 666 Park Avenue below: