Rath was born in Vienna and grew up there. After the Anschluss he came through a Kindertransport as a thirteen-year-old boy to Mandate Palestine. As one of the founders of Kibbutz Hamadia he lived there for 16 years and studied contemporary history and economics.
After turning to journalism he became editor of the Jerusalem Post in 1975, and in 1979 was appointed its Editor-in-Chief. In this capacity he belonged, together with Shimon Peres, to the inner circle of friends of David Ben-Gurion. Leaving the Jerusalem Post in 1989, he was a freelance writer and taught at the University of Potsdam and was news editor of the on-line journal Partners for Peace.
For his merits of Israeli-German/Austrian dialog he was awarded several honors among others: in 2005 he won the German Bundesverdienstkreuz; his latest award for his "dialog between Vienna and Israel" was the Goldenes Ehrenzeichen (golden badge of honor) of the city of Vienna.
In 2005, Ari Rath, along with some British and Arab journalists, received a Special Prize in the British House of Lords in the shape of an olive tree from the International Council for Press and Broadcasting in recognition of his achievement and tireless work for rapprochement and peace. This was in lieu of the Peace for Media awards, which were not given that year.
Rath died on 13 January 2017 in Vienna at the age of 92.