Pellegrino appeared in season 7, episode 3 of The X-Files in November 1999.
In 2001, he played an incompetent hitman in David Lynch's critically acclaimed Mulholland Drive.

Pellegrino starred as Rita's abusive ex-con former husband Paul on Showtime's Dexter; and later as Lucifer on Supernatural and as the mysterious near-immortal Jacob on ABC's Lost.
He has appeared on the television series Northern Exposure, ER, Without a Trace, NYPD Blue, CSI: Crime Scene Investigation, and Knight Rider.

He played the "Blond Thug" who stuffs The Dude's head down the toilet and drops his bowling ball, breaking the floor tile, in the cult film The Big Lebowski.
He was featured in National Treasure as the background FBI agent known as Agent Johnson.
In 2005, Pellegrino appeared in the Academy Award winning film Capote, playing murderer Dick Hickock.

Among his numerous cable and network television show roles, he portrayed terrorist bomber Bobby James on The Beast.

In March 2009, Pellegrino was cast on the ABC series Lost for an appearance in the final episode of Season 5, to play the role of the mysterious Jacob.
Although the press release for the episode refers to his character simply as "Man No.
1", the episode revealed that Pellegrino portrayed Jacob, a mysterious character pivotal to the show's plot.

On June 26, 2009, it was also announced that Pellegrino was cast in a recurring role as Lucifer in the fifth season of the CW series Supernatural until he was returned to his prison, returning in the seventh season as a hallucination of protagonist Sam Winchester due to his mental damage after he spent a year in the Cage, until Sam was cured of his insanity.
Pellegrino reprised his role as Lucifer in season 11's O Brother Where Art Thou?,
The Devil in the Details and Hell's Angel.

He portrayed the vampire "Bishop" in the SyFy horror series Being Human in the first season, and also reprises the role in season 2 and 3 as both flashbacks and hallucinations.

In 2015, Pellegrino joined the ABC thriller series Quantico playing the recurring role of FBI Deputy Director Clayton Haas.

Pellegrino also was featured as a voice actor in the 2018 hit game Far Cry 5 as Jacob Seed, one of the antagonists of the game, as his first role in a video game.
Pellegrino appeared in season 7, episode 3 of The X-Files in November 1999. In 2001, he played an incompetent hitman in David Lynch's critically acclaimed Mulholland Drive.
Pellegrino starred as Rita's abusive ex-con former husband Paul on Showtime's Dexter; and later as Lucifer on Supernatural and as the mysterious near-immortal Jacob on ABC's Lost. He has appeared on the television series Northern Exposure, ER, Without a Trace, NYPD Blue, CSI: Crime Scene Investigation, and Knight Rider.
He played the "Blond Thug" who stuffs The Dude's head down the toilet and drops his bowling ball, breaking the floor tile, in the cult film The Big Lebowski. He was featured in National Treasure as the background FBI agent known as Agent Johnson. In 2005, Pellegrino appeared in the Academy Award winning film Capote, playing murderer Dick Hickock.
Among his numerous cable and network television show roles, he portrayed terrorist bomber Bobby James on The Beast.
In March 2009, Pellegrino was cast on the ABC series Lost for an appearance in the final episode of Season 5, to play the role of the mysterious Jacob. Although the press release for the episode refers to his character simply as "Man No. 1", the episode revealed that Pellegrino portrayed Jacob, a mysterious character pivotal to the show's plot. 
On June 26, 2009, it was also announced that Pellegrino was cast in a recurring role as Lucifer in the fifth season of the CW series Supernatural until he was returned to his prison, returning in the seventh season as a hallucination of protagonist Sam Winchester due to his mental damage after he spent a year in the Cage, until Sam was cured of his insanity. Pellegrino reprised his role as Lucifer in season 11's O Brother Where Art Thou?, The Devil in the Details and Hell's Angel.
He portrayed the vampire "Bishop" in the SyFy horror series Being Human in the first season, and also reprises the role in season 2 and 3 as both flashbacks and hallucinations.
In 2015, Pellegrino joined the ABC thriller series Quantico playing the recurring role of FBI Deputy Director Clayton Haas.
Pellegrino also was featured as a voice actor in the 2018 hit game Far Cry 5 as Jacob Seed, one of the antagonists of the game, as his first role in a video game.
Mark Pellegrino