Hirsch was born in Santiago, Chile, to Jewish-German parents. His mother, Lysa Goldschmidt, arrived in Chile before World War II, while his father, Jorge Hirsch, arrived in the country escaping from German Nazi concentration camps.
Hirsch is married to Juanita Vergara and has two children.
In 1983 Hirsch helped found the Humanist Party, the first political party legalized (1987) under the dictatorship of Augusto Pinochet, and was president of the party from 1994 until 1999. He was also one of the founders of the Coalition of Parties for Democracy (CPD) and served as Chile's ambassador to New Zealand between 1990–92, under the democratic government of Patricio Aylwin. In January 1993, the Humanist Party withdrew from the CPD.