Mourning Grave broke the record of the most attendance for Korean movies released in Mongolia.
Though he specializes in horror films, director Oh In-chun has to have the TV on when he sleeps alone at home since he is very afraid of ghosts.
The main actors Kang Ha-neul, Kim So-eun, Han Hye-rin and Park Doo-sik implied that while the mood of the film in general was grim, the mood on set was actually lively, and in some cases nostalgic as they got to experience what it was like going to school again with wearing a uniform and filming inside a school building. Some of the actors did not know about how strong the message the movie was sending about school bullying, which is still a problem in South Korean schools, to the audience until they watched the final product.
The director and the staff actually encountered ghost while filming.
The snow in one of the romance scenes is drawn with computer graphics.