Viktor's senior national team debut came in 1966 against Brazil at the Maracanã stadium. He represented his nation at the 1970 FIFA World Cup. He was one of the brightest stars at UEFA Euro 1976, where he helped Czechoslovakia win the championship, producing notable performances and key saves against the Netherlands in the semi-final, and West Germany in the final, later being named to the team of the tournament. In the same year he came third in the European Footballer of the Year awards. In total, he made 63 international appearances between 1966 and 1977.