[11] Horn currently lives in the East Gate Bel Air section of Los Angeles, California,[12] with his wife, Cindy Harrell, a former model.

[16] There, he oversaw films including A Few Good Men (1992), The Green Mile (1999), When Harry Met Sally (1989), and the TV sitcom Seinfeld (1989–1998).

[11] Horn became president and COO of Warner Bros. in 1999, where he ran the studio in partnership with chairman and CEO Barry Meyer for 12 years.

Under Horn's leadership, Warner Bros. had many hits, including the Harry Potter series (2001–2011) and Christopher Nolan's The Dark Knight Trilogy (2005–2012).

Starting August 1, 2022, Horn began serving as a business consultant during its transitionary period following the acquisition of WarnerMedia by Discovery, Inc.[5]