He spent most of his playing career in the 1940s and 1950s with Dinamo Zagreb, with whom he won two Federal League championships of Yugoslavia and one Marshal Tito Cup.

Regarded as one of the best defenders in the country at the time, Horvat also earned 60 international caps for Yugoslavia, and was part of the national squad at the 1950 and 1954 World Cups, as well as the 1952 Olympics in Helsinki, where they were silver medalists.

In 1957 he went abroad to join Eintracht Frankfurt, helping them win their first and only West German championship in 1959 before retiring from active football.

In the following year, this time under Paul Oßwald, the club won the 1958–59 Oberliga title and went on to win the 1959 German football championship playoff, although Horvat did not play in the historic final in Berlin, which pitched Eintracht against Kickers Offenbach coached by Horvat's former manager at Dinamo Bogdan Cuvaj.

In the beginning of the 1978–1979 Horvat returned to Schalke but due to the team's bad performances and an embarrassing derby loss against Bochum he was fired in March.