In 1995, he won the Primetime Emmy Award for Outstanding Drama Series for his work on the second season of NYPD Blue.
He began working in the television industry with National Lampoon and HBO as a writer on the short film Disco Beaver from Outer Space in 1978.
and Stiggs a theatrical film based on characters he created with Tod Carrol for National Lampoon and directed by Robert Altman.
Mann worked as a writer on the crime drama The Street, Universal TV's innovative half-hour syndicated faux verite cop show, as well as Stephen J. Cannell's Wiseguy, Miami Vice, and a Saturday morning animated cartoon entitled Slimer!
He became a producer on Steven Bochco's Civil Wars which aired for two short seasons on the ABC network commencing in 1991.
Following which, in 1993 he began working on the ABC police drama NYPD Blue which was created by David Milch and Steven Bochco.
He was again nominated for the Emmy Award for writing for a drama series for his work on "Lost Israel: Part 2" in 1998.
He worked as a supervising producer on Skin, a short-lived modern take on Romeo and Juliet set in the adult-film industry in 2003.
Mann and the writing staff were nominated for a Writers Guild of America (WGA) Award for Best Dramatic Series for their work on the second season.
Mann moved on to work as a co-executive producer and writer for the Starz original drama series Crash.