When Reddick was fourteen, he wrote a ten-page treatment of a prequel to A Nightmare on Elm Street and sent it to New Line Cinema. The studio did not accept unsolicited material, and it was returned unread. Reddick proceeded to contact studio founder Robert Shaye and asked him to read the treatment. Shaye read it and responded. This was the beginning of a letter-and-phone relationship with Shaye and his assistant that lasted for years. While in college, Jeffrey landed an internship at New Line and worked for the studio for almost eleven years.
Reddick is mostly known for writing horror films, but he recently worked on two animated series for Netflix, including a spin-off of the classic Japanese comic book Usagi Yojimbo by Stan Sakai. He is currently adapting the YA book series, The Adventures of Young Captain Nemo. He made his directorial debut with his mystery thriller Don't Look Back in 2020.