Borenstein wrote, edited, and directed the 2003 film Swordswallowers and Thin Men while a senior at Yale University. The film starred Peter Cellini, Zoe Kazan, Fran Kranz and Graham Norris, and featured Army Wives star Sally Pressman and Midnight's Children lead Satya Bhabha. The film won Best Feature and Best Screenplay at the New York Independent Film Festival and was named Best First Feature 2003 by Los Angeles Times critic Kevin Thomas.
Borenstein's 2008 screenplay What Is Life Worth?, based on Kenneth Feinberg's memoir of the same name, was honored with inclusion on the The Black List, an annual list compiled by Hollywood executives of their favorite unproduced screenplays. His 2009 screenplay Jimi, commissioned by Legendary Pictures and based on the life of guitarist Jimi Hendrix, was also included on The Black List. Borenstein wrote additional projects for Legendary, including Godzilla. For future projects, Borenstein will write the sequel for Godzilla and Kong: Skull Island for Legendary, Paladin for Walt Disney Pictures, and Mona for New Regency. In April 2016, Borenstein was announced as an executive producer for HBO's Vinyl's second season.