His notable roles include Duane Duke in Psycho III (1986), Pete Verill in Clint Eastwood's White Hunter Black Heart (1990), Jobe Smith in The Lawnmower Man (1992), and Captain Frank Lapidus on the ABC series Lost (2008–2010).

That same year, Fahey guest starred on the Season 3 premiere of Miami Vice as gun dealer Eddie Kaye, famously destroying Detective Sonny Crockett's Ferrari Daytona.

In 1990, Fahey starred in Impulse and White Hunter Black Heart, respectively directed by feuding ex-couple Sondra Locke and Clint Eastwood.

In 1995, Fahey was the lead in the Trimark Pictures adventure film Eye of the Wolf, directed by Arnaud Sélignac, based on the book "KAZAN" by James Oliver Curwood.

In 2013, a new production of the classic play Twelve Angry Men took place at the Garrick Theatre in London, running until March 2014.

Other notable actors appearing in this production were Martin Shaw who played the part of juror number 8 (a role made famous in the 1957 film by Henry Fonda), Robert Vaughn and Nick Moran.