Mikuljan took a degree in film editing from the Academy for theatre, film and television (today Academy of Drama Arts) in Zagreb. He started to work on film in the mid 60’s as an amateur, gaining recognition as a master of amateur film. Professionally he was engaged in film in the early 70’s as a director of short feature films and documentaries. During the 80’s he made two feature films, Hoću živjeti, portraying contemporary rural life, and Crveni i crni, about the coalminers’ strike in Labin in 1921, and the establishment of the so-called Republic of Labin. For Television Novi Sad he directed the TV-film Smrt godišnjeg doba (1988). At Television Zagreb and later Croatian Radiotelevision, where in the 1990’s he worked as editor of documentary program, he directed many documentaries (e.g. Sudbine: Janko Bobetko, 1992).