In 1976, he was elected secretary general of the new Hadash party, an alliance of Rakah and several other smaller left-wing and Israeli Arab parties, and was elected to the Knesset on Hadash's list in 1977, 1981, 1984 and 1988, before resigning from the Knesset in July 1990 and being replaced by Tamar Gozansky.
In 1976, Arafat and Kaddoumi met with Meir Vilner and Tawfik Toubi, heads of Rakah (New Communist List), which had developed after the 1965 split in the Israeli Communist Party, and from which Hadash eventually developed.