Ben-Aharon was born in the Bukovina region of the Austro-Hungarian Empire (today Romania). He became a leader in Hashomer Hatzair in Romania, and in 1928 he emigrated to Mandate Palestine. From 1932–38, he was Secretary of the Tel Aviv Workers' Council. In the summer of 1935, he served for a few months as the envoy for the Halutz organization in Nazi Germany until he was expelled by the Gestapo. He was a Knesset member from the first to the fifth Knessets and in the seventh and eighth, and a former Minister of Transport and General secretary of the Histadrut.