The film is distributed on 19 prints by 2i Film starting 28 February 2013, Ankica Jurić Tilić, who produced the film through Kinorama  told FNE. She is now developing two more movies inspired by the series of books by Ivan Kusan, The Mystery of Green Hill/Uzbuna na Zelenom Vrhu from director Cejen Cernic, and Love and Death/Ljubav ili smrt, from director Daniel Kusan. Koko and the Ghosts was released on 13 prints by Continental film and had 73,566 admissions in 2011.

The success of The Mysterious Boy comes on the heels of a very promising debut for Croatian films. Vinko Bresan's comedy The Priest's Children set a domestic record opening since Croatian independence. It opened on 3 January 2013 and sold 33,759 tickets on the opening weekend, taking in 144,565 EUR/1,094,851 HRK at the box office. The trend started mid-December 2012 when Vlatka Vorkapic's debut feature Sonja and the Bull set a ten-year record with 9,949 admissions and 40,000 EUR/301,975 HRK in its first weekend.

The Mysterious Boy is the story of fourteen-year old boys who solve a mystery with the help of their resourceful friend Koko. The film was written by Hana Jušića and stars Antonio Parac and Nina Mileta. It is produced by Kinorama and Croatian Radiotelevision, with support from the Croatian Audiovisual Center. The project also received a development grant from MEDIA 2007 Programme.