He played Horace Pinker in Shocker, Walter Skinner on The X-Files, Colonel Steven Caldwell on Stargate Atlantis, Ernest Darby in Sons of Anarchy, and Harris Ryland in the TNT revival of Dallas (2012–2014).

He played the recurring role of character Colonel Steven Caldwell, Commander of the Earth Battlecruiser, Daedalus, in the second (2005) and subsequent seasons of the television series Stargate Atlantis.

In a first-season episode of That '70s Show he played Red Forman's swinger, navy buddy, Bull, alongside his real life wife, Arlene.

Since 2008, Pileggi has played Ernest Darby, the head of a white supremacist gang called the "Nordics", in the FX drama Sons of Anarchy .

He also played spree killer Norman Hill (AKA The Road Warrior) on a season four episode of Criminal Minds, titled "Normal".

Pileggi also hosted the Fox specials Breaking the Magician's Code: Magic's Biggest Secrets Finally Revealed and Conspiracy Theory: Did We Land on the Moon?.

[7] As of 2014, Pileggi is on the advisory board of Sci-Fest, the first annual Los Angeles Science Fiction One-Act Play Festival, held in May 2014.