Mihok got his start doing guest spots in local New York City productions of Law & Order, NYPD Blue, and New York Undercover. In 1994, Mihok debuted in the independent film, Black is White. In 1995, Mihok appeared in the CBS movie of the week, Murderous Intent.
In 1996, Mihok was a featured regular in the role of Joey in the Rhea Perlman CBS sitcom Pearl.
In 1997, Mihok met Alanis Morissette through friend Leonardo DiCaprio during a trip to Cuba. The lyrics to the songs "So Pure" from Supposed Former Infatuation Junkie and "That Particular Time" from Under Rug Swept are about him.
In 1998, for Terrence Malick's Thin Red Line, Mihok said he spent an intensive six months working on the film, with the amount of footage constituting a full starring part, but during editing was reduced to an ensemble role as Private First Class Doll. Mihok is slated to direct an episode in 2017, as he said he has been directing pilots to prepare.
In 1999, Mihok appeared on The WB series Felicity, where he portrayed Lynn, a competitive Swimmer, in multiple episodes.
In 2004, Mihok appeared on Sicilian-Puerto Rican New York-based Rapper Sabac Red's record Sabacolypse: A Change Gon' Come, on the track "I Have A Dream." The lyrics refer to tics that people exhibit as symptoms of Tourette syndrome.
In 2006, Mihok appeared in the film Hollywoodland and in 2007 in the film, Firehouse Dog.
In 2008, he played Detective Martin Soap in the film Punisher: War Zone.
In 2009, Mihok married singer Valeria Mason. They have two children and live in Los Angeles. Mihok has said that he is Catholic.
As part of the 2011 straight-to-video film, Lifted, Mihok and the actor who plays his son in the film, Uriah Shelton, recorded a song called "I Miss You." The film features many musical and dance performances by Mihok.
Since 2013, Mihok has co-starred as Brendan "Bunchy" Donovan in the Showtime drama Ray Donovan. Bunchy has been sexually abused by a priest and is an alcoholic and suffers from sexual anorexia. For the show the cast works out at the Santa Monica, California boxing gym Wild Card West with boxer Rob Garcia.
In 2014, he portrayed Whelan, in the horror-thriller film, Before I Wake, co-starring in the Mike Flanagan-directed film Annabeth Gish, Thomas Jane and Kate Bosworth.
The 2015 video for Love (feat. Jeff Taylor) features many actors from Ray Donovan.
In 2016, Mihok appeared in the film, So B. It, which stars Alfre Woodard, Cloris Leachman, Jacinda Barrett, and John Heard.
Also in 2017, Mihok plays a car salesman in the film Car Dogs, which features Patrick J. Adams, Octavia Spencer, Josh Hopkins, among others.
