Born in Camp Zama, Japan, he received a B.A. in English literature from UCLA and an M.F.A. in screenwriting from the American Film Institute.

Spotnitz began his career as a newspaper and magazine writer, working for the Associated Press, United Press International and Entertainment Weekly, among others.

Joining The X-Files as a writer in 1994, Spotnitz quickly became involved not only in developing the series’ stand-alone episodes, but its elaborate “mythology” storyline dealing with government conspiracy and aliens. He directed two episodes and wrote or co-wrote more than 40 installments, including the Emmy-nominated “Memento Mori” (with Chris Carter, Vince Gilligan, and John Shiban) in 1997. Other honors accorded Spotnitz for his work on the series include Golden Globe wins for Best Dramatic Series, a Peabody Award, and three Emmy nominations for Outstanding Drama Series.

Spotnitz worked on The X-Files for eight of its nine seasons, including four years as executive producer and three as president of Carter’s Ten Thirteen Productions. After The X-Files ended its run in 2002, Spotnitz served as executive producer alongside director Michael Mann of the critically acclaimed CBS crime drama Robbery Homicide Division.

In 2006, Spotnitz co-wrote and created (with Vince Gilligan) a pilot for Spike TV called A.M.P.E.D. Spotnitz "re-imagined" the classic Night Stalker TV series for ABC and Touchstone Television in 2005.

His other credits include co-executive producer of Millennium (1996-1999) and executive producer of Harsh Realm (2000) and The Lone Gunmen (2001), which he also co-created. He also co-produced and co-authored the story for the feature film Fight the Future (1998), and produced and co-wrote the 2008 sequel I Want To Believe. He has also signed a three comic deal with Wildstorm to produce three X-Files comic books, the first being released two weeks before the film (although it is not an adaptation).