When he returned to Israel, Yahav became active in politics. He was an advisor to Minister of TransportGad Yaacobi and the spokesman of Teddy Kollek, mayor of Jerusalem. In 1996 he was elected to the Knesset on the Labor Party list, and served as the chairman of the subcommittee for banking. However, he lost his seat in the 1999 elections.
Yahav later left Labour and joined Shinui. In 2003, he was elected mayor of Haifa on a joint Shinui-Greens ticket, having already served as deputy mayor. On 29 June 2006 he defected to Kadima, but remained mayor of the city. He is also chairman of the Haifa Economic Corporation and previously chaired the Haifa International Film Festival organisation and the city's theatre executive.
Published works
The Anatomy of the Fall of the Labor Party with Shevah Weiss (1977)
Libel and Slander (1987, updated and re-released in 1996)