At age 12, Eitan joined the Haganah, forerunner of the IDF, from which he moved to the elite Palmach upon completion of high school in 1944. Through clandestine operations, he was to assist the illegal immigration of Jewish refugees from Europe, who were fleeing Nazism, into Palestine.
During the Israeli War of Independence (1948-49), Eitan served in army intelligence, and afterwards in the newly established Israeli secret service, the Mossad and later as Chief of Operations of the Shin Bet, the Israel Security Agency. In 1960, he was in charge of the Mossad operation that led to the capture of Adolf Eichmann. Eitan was also involved in the secret planning and implementation of the attack on the Iraqi Osirak nuclear reactor in June 1981.
Eitan was appointed as advisor on terrorism to Prime Minister Menachem Begin in 1978, and in 1981 was appointed to head the Bureau of Scientific Relations. In that capacity, Eitan assumed responsibility for and resigned over the Jonathan Pollard affair, and the Bureau was disbanded. From 1985 until 1993, he was head of the government-owned Israel Chemicals Ltd. After 1993, he became a businessman, noted for several large scale agricultural and construction ventures in Cuba.
He was married and the father of three.