Nemec was born and raised in a Jewish family[2] in Yonkers, New York, where he attended Riverdale Country School with longtime writing and producing partner Josh Appelbaum.
Recognized for his writing talent by J. J. Abrams, Nemec spent three years working on ABC's Alias, where he rose to the level of co-executive producer.
Nemec was then re-approached by friend and colleague J. J. Abrams to write Mission: Impossible – Ghost Protocol, the fourth installment in the multibillion-dollar film franchise starring Tom Cruise.
Nemec and Appelbaum also remain active in television where they are writing and developing (with longtime collaborators and friends Scott Rosenberg and Jeff Pinkner) under their banner MIDNIGHT-RADIO.
He frequently collaborates with a tightly knit group of film professionals which include J. J. Abrams, Damon Lindelof, Adam Horowitz, Alex Kurtzman, Roberto Orci, Edward Kitsis, Jeff Pinkner, and Bryan Burk.