Falchuk was born in Massachusetts, to Jewish parents. His mother is Nancy Falchuk, the national president of the Hadassah Women’s Zionist Organization of America from 2007 to 2011. In high school, he tried to stand out from his classmates by wearing a tie to school each day. he also played baseball, basketball and lacrosse. He said, “I was always trying to look smart because I didn’t feel smart”; he actually suffered from undiagnosed dyslexia. He graduated from Hobart and William Smith Colleges in 1993.

Falchuk’s first wife was television producer Suzanne Bukinik, whom he began dating in 1994. The couple were married in 2002 and had two children. They filed for divorce in 2013. Falchuk began dating actress Gwyneth Paltrow in 2014, whom he met on the set of Glee in 2010. The couple went public with their relationship in April 2015 at a birthday party after months of speculation. On January 8, 2018, Paltrow and Falchuk announced they had become engaged. In July 2018, the couple announced their “private and small” wedding would be held in September 2018, in The Hamptons, New York, on Long Island, which has since taken place.

In 1997, as a student at the American Film Institute, Falchuk co-founded the arts education nonprofit Young Storytellers, with Mikkel Bondesen and Andrew Barrett in response to cutbacks in funding for creative arts programs in Los Angeles Unified School District. Falchuk currently serves on the Young Storytellers advisory board of directors.

Falchuk’s career in television began as a writer for Mutant X (2001), Earth: Final Conflict (2001–02) and Veritas: The Quest (2003), before he was hired to work on the first season of Nip/Tuck in 2003. While working on Nip/Tuck, he formed a close bond and partnership with the show’s creator, Ryan Murphy. Falchuk and Murphy went on to write a television pilot titled Pretty/Handsome, about a transgender gynecologist, which the FX network bought in 2008. However, the pilot was not picked up as a series.

As Nip/Tuck neared its sixth and final season, Falchuk and Murphy began to look for their next project, and decided to focus on a lighter subject. They teamed up with Ian Brennan, who had written a screenplay about high school show choirs, to pitch a one-hour comedy about a glee club to the Fox Broadcasting Company. Their pitch was successful and turned into the television show Glee, which premiered in 2009. Falchuk, Murphy and Brennan received two Writers Guild of America Award nominations for Best Comedy Series and Best New Series.

In 2011, Falchuk co-created the FX horror-drama anthology series American Horror Story with previous collaborator Ryan Murphy. The first season, starring Jessica Lange, Connie Britton and Dylan McDermott, premiered October 5, 2011, and received critical acclaim; the series was nominated for 17 Primetime Emmy Awards in 2012, and 15 Primetime Emmys in 2013, with Falchuk nominated for Outstanding Miniseries or Movie both years. In 2014, the show was once again nominated for 17 Primetime Emmy Awards, with Falchuk nominated for Outstanding Writing for a Miniseries, Movie or a Dramatic Special.

Falchuk’s brother, Evan Falchuk, founded the United Independent Party and was a candidate for governor in the 2014 Massachusetts gubernatorial election. In 2008, Falchuk was diagnosed by his father and brother’s medical consulting firm as having a serious problem with his spinal cord. After undergoing emergency spinal surgery he made a full recovery, and his experience inspired parts of the Glee episode “Wheels”.

In March 2019, Falchuk signed a four-year overall deal with Netflix through his Brad Falchuk Teley-Vision production company to “develop, write, produce, and direct new series”.