Born in Jerusalem, Eichler worked as an author and journalist. He became editor of HaMahane HaHaredi in 1980, and in 1996 became chairman of the Centre for Jewish Publicity.
A member of Agudat Yisrael, in 2003 he was elected to the Knesset on the United Torah Judaism list (UTJ being an alliance of Agudat Yisrael and Degel HaTorah). The alliance split in January 2005. He resigned from the Knesset on 23 February that year and was replaced by Shmuel Halpert.
As part of a seat rotation agreement within United Torah Judaism, he returned to the Knesset on 6 February 2011 as a replacement for Meir Porush.