Yedioth Ahronoth was established in the late 1930s by an investor named Nachum Kumarov. It was the first evening paper in the British Mandate of Palestine, and attempted to emulate the format of the London Evening Standard. Running into financial difficulties, Kumarov sold the paper to Yehuda Mozes, a wealthy land dealer who regarded the paper as an interesting hobby and a long-term financial investment. His sons, Reuben and Noah ran the paper with Noah as the first managing editor.
In 1948, a large group of journalists and staff members led by chief editor Ezriel Carlebach left to form Yedioth Maariv, later known as Maariv. Carlebach was replaced by Herzl Rosenblum. This began an on-going battle for circulation and prestige between the rival newspapers, which peaked during the 1990s when both papers were discovered to have bugged one another's phones