[3] Horvat was born in Kotoriba, Međimurje, northern Croatia, at the time in Zala County in Hungary.

During World War II he fought in Yugoslav Partisans, which later inspired the novel Mačak pod šljemom (Tomcat under a Helmet, 1962) which had a somewhat ironical view of the partisan movement, adapted both into a feature film and a miniseries.

The screenplay Ciguli Miguli (1952), critical of bureaucracy, briefly brought him into disfavour with the Communist party authorities, on which occasion he turned to sailing.

After a period of deep crisis Horvat published two acclaimed novels inspired by these events, Operacija "Stonoga" (Operation "Centipede", 1982), about a search for a lost island in the Atlantic, and Waitapu (1984), about a Pacific Islander boy who decides to sail across a taboo line.

[3][4][5][6] Horvat attended the Faculty of Philosophy in Zagreb and served as a secretary of Matica hrvatska.