Brett Mullen was born in 1985 in Hornell, New York, to Laura Mullen (Coleman), a horse show manager and event planner, and John Mullen, a floor covering specialist. Brett spent his younger years in Hammondsport, New York and later in Orlando, Florida, where he obtained a degree in Computer Science at Full Sail University and education at The New York Film Academy. In 2008 Mullen relocated to North Carolina to pursue his career.

Brett began his career as a cinematographer, carrying out duties as director of photography on Christine Parker's Dead of the Night (2009) and Matthew B. Moore's Keep it in Hell (2010) in which both films received awards for 'Best Cinematography'. Mullen later collaborated with Moore as producer and director of photography on a western horror feature titled Hatchet County (2012).

In 2014, Mullen directed his first feature film, Bombshell Bloodbath, a graphic zombie horror film, inspired by the late 1970's and early 1980's in Italian cinema. Bombshell Bloodbath was a micro budget film, however, it quickly gained popularity for it's retro charm and grotesque death scenes. Bombshell Bloodbath, marked Brett Mullen's first distribution deal in the United States of American, later receiving distribution in the United Kingdom and Italy under the title, Dead Inferno, portending his future career in horror.

For the following two years, Brett returned to his roots and worked as camera operator on a series of projects including Fix It In Post (2014), Don't Let The Light In (2015) and Maid to Order (2016). During this time, Brett established the production company, Red Nebula, which added a namesake to his future films. In 2017, Mullen and Moore teamed up again to co-produce, Hellions Rise, where Mullen acted as directed of photography.

Mullen's first major directorial effort was his sophomore film, Fantasma (2018), a vibrant Giallo, with horror icons Caroline Williams and Debbie Rochon. Although the film received a shocking title change to 'Bloody Ballet' from High Octane Pictures, Fantasma placed Mullen's name in a surfeit of horror publications, including Videoscope, Scream, Asylum and Delirium Magazine.

During the anticipated release of Fantasma, Brett Mullen teamed up with writer Bill Mulligan to create a Giallo horror short titled, Belladonna (2018), aimed at the film festival circuit. Belladonna, has cemented 15 awards and nominations to date, including best cinematography, best director, best visual FX and best film.