[2] He attended the lower classes of a Franciscan gymnasium in Sinj, and continued his high school education in Osijek.
Before World War II, he joined the Young Communist League of Yugoslavia (SKOJ).
In 1967, after Franjo Tuđman was arrested because of undesirable political activity, Bilandžić succeeded him as the director of the Institute for the History of the Workers' Movement in Croatia.
He was a dean on the Faculty of Political Science at the University of Zagreb at the end of the 1970s and the beginning of the 1980s.
Since he denied the validity of Yugoslav nationality during the 1981 census, he was highly criticized by Belgrade as a separatist and Ustaše.
In 2004, in a popular Croatian talk show, Nedjeljom u 2, Bilandžić stated that Croatia had more sovereignty in the SFR Yugoslavia than it would have in the European Union.