The film is inspired by the 2005 film "A History of Violence" by David Cronenberg. According to Lokesh, "It inspired me to write "Leo". A History of Violence (2005) left its mark on me and from that this movie was born. "Leo" is my tribute to Cronenberg's film".
To prove that he's not Leo Das, Parthiban shows Harold pictures of his childhood and family, most of which are real life photos from actor Vijay's personal life.
Movie was initially planned to shoot in Moonar and later moved to Kashmir. Movie was shot for 120 days in Kashmir.
Maya S. Krishnan, who portrays an unnamed escort in the Lokesh Cinematic Universe (LCU) franchise, served as the Tamil language coach for actor Sanjay Dutt on the sets of this film.
The title card is shown only at the interval point of the film.