Movie was rereleased in South Korea on December 31, 2015 as "Inside Men: The Original." The rereleased version contains additional footage accounting for 50 more minutes (3 hour total runtime).
Based on webcomic "Naeboojadeul" by Yoon Tae-Ho (first published November 9, 2010 via website The Hankyoreh).
Filming began July 13, 2014 at a night club in Seoul, South Korea. The first scene filmed involved gang member An Sang-Go (Lee Byung-Hun) meeting newspaper writer Lee Gang-Hee (Baek Yoon-Sik).