As an actor, Pollak's most notable roles are usually playing the best friend or confidant characters to the leading men, as he did in Ricochet (1991), A Few Good Men (1992), End of Days (1999), and The Wedding Planner (2001). However, he has also played a wide variety of parts, such as a Criminal in The Usual Suspects (1995) and a gangster in The Whole Nine Yards (2000). He also briefly hosted Celebrity Poker Showdown in its first season. His most substantial role to date was in Deterrence (1999), in which he played the main character, a Vice President who must take over for a deceased President and deal with a nuclear crisis.

As a Comedian, Pollak's most famous work was his 1992 HBO special Stop With the Kicking, directed by fellow Comedian David Steinberg and produced by comedy Writer Martin Olson. In July 2009, The Littlest Suspect, his most recent comedy special, was aired on Showtime. Comedy Central named Kevin as of the Top 100 Comedians of All Time.

In December 2006, he played Karl Kreutzfeld in the Sci Fi Channel miniseries The Lost Room. Through 2008, he had a recurring role as a District Attorney on the television series Shark. In March 2008, Pollak played himself in the web series The Writers Room on Crackle. In 2010, he portrayed Sheriff Tom Wagner in Choose.

In April 2009, Pollak partnered with Jason Calacanis on a weekly Internet talk show, Kevin Pollak's Chat Show. Guests for the show include film Directors Kevin Smith and Mike Binder, comedians Jimmy Pardo and Bill Burr, and actors Nia Vardalos, Illeana Douglas, Bryan Cranston, Dana Carvey, Matthew Perry, Jon Hamm, Paul Rudd, Adam Carolla, Anthony Cumia, Jason Alexander, Seth MacFarlane, Tom Hanks, and Jason Lee.

In January 2010, Pollak was scheduled to host Our Little Genius on FOX, but the series was pulled before it could air on television. Pollak was then seen hosting Million Dollar Money Drop, again on the FOX network at the end of 2010.

In 2012, Pollak began a new podcast called Talkin Walkin in which he spends an hour or more with a new guest in character as Christopher Walken. After three episodes, the show was rated in the top 5 of all comedy podcasts by iTunes.

In 2014, Pollak began a recurring role as Alvin Biletnikoff on the CBS sitcom Mom. However, his time on the show was cut short by the death of his character.

Pollak's directorial debut was on the horror web series Vamped Out, featured on the internet television platform Babelgum. Jason Antoon, Seana Kofoed, Samm Levine and Pollak all acted in the ensemble cast. The screenbook was based on a simple joke that Antoon and Pollak had between them. Most recently, Pollak's feature film directorial debut, the comedy documentary Misery Loves Comedy, premiered at the 2015 Sundance Film Festival. The film sold North American rights to Tribeca Film, a US distribution company.

Pollak directed the comedy film The Late Bloomer, which was released in 2016.

In 2017, Pollak joined the cast of the Golden Globe winning The Marvelous Mrs. Maisel, an original series from Amazon, as Moishe Maisel, the main character's father-in-law.

He is the only person to ever go "2 for 2" (two exact matches), as a guest on the Sklar Brothers/Daniel Van Kirk podcast Dumb People Town, in the "Guess the Age" game. The feat was completed on the episode released on April 2, 2018.