He read magazines like Fangoria and attended genre movie screenings, including the original Dawn of the Dead at the Tivoli Theatre in St. Louis.

[25] Gunn said that, at an unspecified time in his college education, "I went to two years undergraduate film school at Loyola Marymount in Los Angeles.

The group released the album Mom, We Like It Here on Earth in 1994, and its songs "Sunday" and "Walking Naked" were featured in the film Tromeo and Juliet.

Gunn began his career in filmmaking with Troma Entertainment in 1996, for which he co-wrote the independent film Tromeo and Juliet.

[23] After contributing to several other Troma films, Gunn in 2000 wrote, produced and performed in the superhero comedy The Specials, directed by Craig Mazin and featuring Rob Lowe, Thomas Haden Church, Paget Brewster, Judy Greer and Jamie Kennedy.

His film directorial debut was the 2006 horror-comedy Slither, which was included on Rotten Tomatoes' list of the 50 Best Ever Reviewed Horror Movies.

In 2008, Gunn was a judge on the VH1 reality television show Scream Queens, where 10 unknown actresses compete for a role in the film Saw VI.

"[34] In 2010, Gunn released Super, a dark comedy and superhero satire starring Rainn Wilson and Elliot Page.

After Dan Gilroy and Jack Black separately lamented the proliferation of superhero films,[36] Gunn responded in a Facebook post, saying in part:Popular fare in any medium has always been snubbed by the self-appointed elite.

[38] In 2016, he directed three Stan Lee cameo scenes in one day, for the film Doctor Strange and two unrevealed projects.

3 in July 2018, but before the project started, Disney severed ties with Gunn as the director amid controversy over off-color jokes he had tweeted.

[49] He also wrote, directed, and produced the spin-off television series for the film centered on the character Peacemaker played by John Cena for Max.

[53][54] Amid criticism of the tweets, Disney severed ties with Gunn as the director of the upcoming Guardians of the Galaxy Vol.

"[55][56] Walt Disney Studios's decision received criticism from many entertainers and journalists, including actors Dave Bautista, Selma Blair, Patton Oswalt, David Dastmalchian, Michael Ian Black, Mikaela Hoover, Mike Colter, Alex Winter, David Hasselhoff, directors Joe Carnahan and Fede Álvarez, comics artist Jim Starlin, musician Rhett Miller, comedian Jim Jefferies, Rick and Morty creators Justin Roiland and Dan Harmon, journalist David A. French and Troma Entertainment founder and president Lloyd Kaufman.

[66] A number of media outlets criticized Disney's decision, including Collider, Cartoon Brew, The Daily Dot, The Independent, National Review, MovieWeb, and Vulture.

[57][73][74][75] On July 30, 2018, Guardians of the Galaxy cast members Chris Pratt, Zoe Saldana, Dave Bautista, Bradley Cooper, Vin Diesel, Sean Gunn, Karen Gillan, Pom Klementieff and Michael Rooker released a joint statement through social media expressing their support for Gunn.

[76] Because of the situation, Sony Pictures decided to not promote the horror film Brightburn, which Gunn produced, at the 2018 San Diego Comic-Con.

[46] Gunn and frequent producing partner Peter Safran had advised David Zaslav, the CEO of the newly created Warner Bros.

[84] In January 2023, Gunn and Safran revealed their plans for future DCU films, with the first chapter being titled "Gods and Monsters".

Gunn also wrote a seven-episode animated series titled Creature Commandos, based on the comic book team of the same name,[85] and also worked on the HBO Max series Waller, a spin-off of Peacemaker focusing on the character of Amanda Waller, with Christal Henry writing and Viola Davis reprising her role from previous DCEU projects.

[86][87] Gunn is also involved in multiple other DC projects, including producing Supergirl: Woman of Tomorrow due for release in 2026.

[96] Gunn was raised in a Catholic family and has mentioned how prayer continues to play an important role in his life,[97] but has also said that he is, "in some ways, anti-religion".