Hollai joined the Hungarian foreign service in 1949. He served as Hungary's deputy representative to the United Nations from 1956 to 1960, as the head of foreign relations for the Central Committee of the Hungarian Communist Party from 1960 to 1963, as Hungary's ambassador to Greece and Cyprus from 1964 to 1970, and as Hungary's deputy foreign minister from 1970 to 1974. He served as Hungary's ambassador to the United Nations from 1974 to 1980.