Proops has performed his stand-up act across Britain, mainland Europe, Australia and New Zealand. His other credits include hosting Space Cadets, a mid-1990s science-fiction comedy game show on Channel 4 in the UK, which also featured Craig Charles (Dave Lister from Red Dwarf) and Bill Bailey, and appearances on BBC2’s Mock the Week. He appeared as a panelist on the 2000 revival of To Tell the Truth. Proops has also hosted game shows, including VS. in 1999, Rendez-View in 2001, and Head Games, a Science Channel game show which ran for one season in 2009.

In addition to his stand-up and improv acts, Proops has done voice work in various films and TV shows, including Tim Burton’s The Nightmare Before Christmas, and the miniseries Stripperella with Pamela Anderson. He provided the voice for the Fode, the Galactic Basic speaking half of the two-headed Pod-Race announcer in Star Wars: Episode I – The Phantom Menace, with Scott Capurro providing the voice for the other, Huttese-speaking half, Beed. Proops provided the voice of Bob in the US version of the TV series Bob the Builder for the five seasons of Project Build It. He has also featured in 2003 film Brother Bear as the voice of one of the Love Bears and provided the voice as Cryptograf in 2006 film Asterix and the Vikings.

From 1995–1996, Proops presented Bits from Last Week’s Radio on BBC Radio 1. He did voice work for the BBC Radio 2 series Flight of the Conchords, first broadcast in September 2005. Proops also played the title role in BBC Radio 4’s sci-fi comedy series Seymour the Fractal Cat.

Since 2010, Proops hosts a podcast called The Smartest Man In The World, often together with his wife Jennifer Canaga, in which he talks about current events, celebrity culture, and his personal life, usually in front of a live audience. Before Smartest Man, Proops hosted a podcast called The Greg Proops Experiment.

Proops also appeared in every episode of the short-lived Drew Carey’s Green Screen Show, where the performers would play improv games (some of which were taken from the show’s main influence Whose Line Is It Anyway?) in front of a massive green screen. Later, animators would draw on the background and other props. In April 2011, Drew Carey’s Improv-A-Ganza premiered on GSN featuring Proops along with other frequent guests from Whose Line is it Anyway? In July 2012, Proops appeared in ABC’s improvisation show, Trust Us with Your Life.

In November 2011, Proops did a week on Royal Caribbean’s Freedom of the Seas with the Lewis Black Comedy Cruise Tour. He performed the entire week of stand-up with other artists, which included a live, one-hour podcast in front of his entire audience.

On May 5, 2015, Proops released nonfiction book The Smartest Book in the World through publisher Touchstone. The book is based in part on Proops’s weekly podcast The Smartest Man in the World, detailing the author’s movie and poetry recommendations, baseball facts, powerful women, and misconstrued history. The paperback version of the book was released from Touchstone on February 21, 2017.

Proops has been involved with Turner Classic Movies since 2013, appearing on several of the network’s podcasts and in person at public events. In 2016, he appeared as a television presenter for TCM, introducing comedy films by the Marx Brothers and Wheeler & Woolsey.

Proops has been involved with the Star Wars franchise as well. He played the role of Fode in Star Wars: Episode I – The Phantom Menace. He would later work with the Expanded Universe, reprising his role as Fode in the video game Star Wars Episode I: Racer and the video game adaptation of Star Wars Episode I: The Phantom Menace, and he guest-starred on two episodes of the animated series Star Wars: The Clone Wars (“The Mandalore Plot” and “Voyage of Temptation”) as Tal Merrick. In 2018, Proops voiced Jak Sivrak in Star Wars Resistance.