Horn, a New York native, had "a grim, grinding, achingly humorless childhood only Charles Dickens could do justice to," according to writer Harry Haun.
After moving to Los Angeles, Horn was signed to an overall production deal with Warner Brothers Studios, where he developed, wrote, and executive produced dozens of network pilots and series.
[4] Special projects include The RuPaul Christmas Special on BBC, Bette Midler's Divine Intervention Tour, and a digital musical series co-written with Jason Robert Brown for Sony's digital Crackle network.
Horn's work on Tootsie received widespread acclaim upon the musical's pre-Broadway premiere in Chicago – Vanity Fair says "the humor of Tootsie arises from writer Robert Horn’s bull’s-eye deployment of zingers – and the cast’s infallible delivery of them.
For Shucked, Horn received Tony, Drama Desk, and Outer Critics Circle nominations for Best Book.