The son of poultry vendors, he was educated at a religious school. In his teens, after initially joining Ze'ev Jabotinsky's Betar organization, he became a member of all three Jewish underground military organizations in British Mandatory Palestine: Lehi (the "Stern Gang"), Etzel, and Haganah (Palmach) that fought the British and the Arab populations. He was arrested by the British Mandatory authorities and spend several months in detention at Latrun. With the establishment of Israel, he briefly joined the Israeli Communist party. He fought in the first three wars: 1948-50, 1956, and 1967. He strongly disagreed with the annexation of the Golan Heights and East Jerusalem and takeover of the West Bank and Gaza Strip by Israel in the aftermath of the Six-Day war.
After the Six Day War, he became famous for a declaration he published in Ha'aretz, together with 11 co-signatories, protesting the incipient occupation. In part it read:-
"Our right to defend ourselves from extermination does not give us the right to oppress others. Occupation entails foreign rule. Foreign rule entails resistance. Resistance entails repression. Repression entails terror and counter-terror. The victims of terror are mostly innocent people. Holding on to the occupied territories will turn us into a nation of murderers and murder victims. Let us get out of the occupied territories immediately.'
He subsequently left Israel in protest, and took up residence in England. Tzabar was a columnist for a number of years for both the daily "Haaretz" and the weekly "Ha'olam Haze" newspapers. He also published 27 books in Hebrew, among these are works of fiction, travel, children's books and poetry. Allan Lane, the hard cover "Penguin", published his English book: "The White Flag Principle" that had been translated and published in Japan and in most European languages.
In 2004, Michelin threatened to sue him for trademark infringement, after he published a study of Israel's prisons under the title "MUCH BETTER THAN THE OFFICIAL MICHELIN Guide to Israeli prisons, Jails, concentration camps and torture chambers"; they eventually dropped the case, much to Tzabar's disappointment. 
An accomplished painter, polymath, and mycophile, he identified one species of mushroom.
Partial bibliography 
- The White Flag Principle: How to Lose a War (and Why), New York 2003, ISBN 978-1-56858-259-7
- Yemenite and Sabra Cookery, (with Naomi Tzabar) Tel-Aviv 1979, ISBN 978-965-234-001-6
- An Illustrated Key for the Identification of Wild Mushrooms, Fungi and Toadstools Interactive CD-Rom, 
- Tusbarahindi the Great
- Shimon Tzabar Memorial website
- Israel Imperial News
- Obituary in Haaretz, 21 March 2007
- Obituary in The Independent, 24 March 2007
- Obituary by Moshé Machover in Hagada Hasmalit (The Left Bank), 22 March 2007
- Moshe Machover and Elizabeth Nussbaum, ‘ Shimon Tzabar,’ The Guardian Monday April 2, 2007
- Traubmann, Tamara. "Shimon Tzabar, 81, Dies in London". 22 March 2007. Ha'aretz. Retrieved 28 Mar. 2009. http://www.haaretz.com/hasen/spages/840080.html
- Michelin sue over 'guide to jail', BBC website, 18 October 2004