He joined the U.S. Coast Guard in 1992. During his enlistment, Brunetti moved to New York. He met actor Kevin Spacey through a chance introduction from a mutual friend while Brunetti was working at a start up digital wireless network company.

Shortly after meeting each other in 1997, Spacey hired Brunetti as his executive assistant. Brunetti worked with Spacey through several feature films, such as American Beauty (1999) and The Shipping News (2001).

In 2001, Brunetti transformed Spacey's Trigger Street Productions website, TriggerStreet.com, originally a static homepage for Trigger Street Productions, into a platform for aspiring filmmakers. The site was a place for users to submit screenplays and short films for feedback from other members. TriggerStreet.com was relaunched in 2002 as an early social media site, hosting member profiles, providing member ratings of submitted work and interactive forums. TriggerStreet steadily gained users resulting in it being named one of the top 50 best websites of 2004 by Time Magazine. The site became known as TriggerStreet Labs and expanded to include short story submissions, it closed down in 2015.

In 2002, Brunetti co-produced the documentaries Uncle Frank and America Rebuilds: A Year At Ground Zero through TriggerStreet. The controversial unreleased documentary Hackers Wanted was also part of the early film slate of the company.

Brunetti's first feature film producing credit was as co-producer for Beyond the Sea (2004). His first full feature credit was Mini's First Time. He later produced the film The Sasquatch Dumpling Gang (2006). He also produced the Emmy-nominated Bernard and Doris.

Brunetti, a Star Wars fan himself, eagerly produced the Star Wars comedy Fanboys. The film was distributed by The Weinstein Company, and originally slated for release on August 17, 2007. However, after delays for re-shoots and disagreements over the film's final cut, the release for Fanboys was delayed until February 9, 2009. Brunetti discussed the film's struggles with The Weinstein Company in interviews on KCRW's The Business podcast and in The New York Times.

Brunetti's first major success was for 21 (2008), a film based on Ben Mezrich's New York Times best selling book Bringing Down The House. Produced on a budget of $35 million, the film went on to a worldwide gross of nearly $158 million.

In early 2009, Brunetti teamed with Mezrich on an adaption of The Accidental Billionaires, which told the story of the founding of Facebook.com. The screenplay adaptation was written by Aaron Sorkin and directed by David Fincher.

In July 2011, at an event at the Talenthouse in Palo Alto, California, Brunetti offered the audience his perspective on working on House of Cards and told the audience, “...Silicon Valley should start making content... Netflix creating original content is a game changer." Brunetti also told the audience that he thought Amazon, Hulu and Fandor would join Netflix in producing their own content, which would lead to subscription cable companies (like HBO) to offer a la carte content in the next 5 years. In May 2012, Amazon announced plans to create original content. Hulu also announced similar plans in 2012. In August 2012, HBO began a la carte subscriptions for their Service in Norway. In early 2013, Verizon unveiled plans to offer cable channels a la carte to consumers.

He went onto have a long-term relationship with costume designer Johanna Argan from prior to 2005 which ended amicably in 2013. The couple have a daughter, Estella, born October 10, 2012.

Brunetti and Kevin Spacey's Trigger Street Productions released their series, House of Cards, on Netflix in early 2013. The entire 13-episode first season was released on Netflix simultaneously.

In 2014, Brunetti sat down with former Facebook executive Randy Zuckerberg for an interview at SXSW Film Festival about the Future of media, personal branding online, and how Hollywood and Silicon Valley continue to converge. On the subject of crowdfunding, Brunetti suggested it was "a genius idea that's gotten a little out of hand...I think it’s wrong when people like Zach Braff or Spike Lee utilize that same Service to fund their films when they already have access," he added. "I think it overshadows the little guys who actually need the funding."

Brunetti produced Captain Phillips, which starred Tom Hanks and was directed by Paul Greengrass, which earned him his second career Academy Award nomination. In 2015, Brunetti and Michael DeLuca reunited to produce the Fifty Shades of Grey film adaptation for Focus Features. In 2016, Brunetti publicly criticized the Producers Guild of America for initially not awarding him a producers mark (p.g.a. mark) for the sequel to Fifty Shades of Grey, Fifty Shades Darker. Brunetti eventually received the mark after he won a decision on appeal. He dubbed it a victory. He was also credited on the third film, Fifty Shades Freed.

When the paperwork for the studio was filed for the court it emerged that Spacey had opted out of assuming the chairmanship of the studios, and by the end of 2016 Brunetti had also left Relativity whilst both remained Executive Producers on House of Cards and Manifesto.