Returning to Lithuania to complete his studies, Unterman was ordained as a rabbi by Rabbi Refael Shapiro, and by Rabbi Simcha Zelig Reguer, the Dayan of Brisk.
He founded  his own yeshiva in the town of Vishnyeva around 1910.
Unterman served a variety of roles in the Lithuanian Jewish community until 1924, when he was selected to become the head rabbi of Liverpool.
Unterman served in Liverpool for 22 years, becoming an important figure in the English Zionist movement and working to relieve the suffering of refugees in England during the Second World War.

In 1946, Unterman became the Chief Rabbi of Tel Aviv, a position he held for twenty years before being appointed Chief Rabbi of Israel.
As Chief Rabbi, Unterman worked to reform the rabbinic court system and reach out to secular Israelis.
He also wrote opinions on a variety of religious issues relevant to the young Jewish state, such as religious conversion and marriage law.

He founded two advanced Talmudical academies (kollels), one in Tel Aviv and one in Jerusalem, designed to prepare select students for the rabbinate and educational positions, with an emphasis on systematic study of Talmud and practical halakhah.

Rabbi Unterman died on January 26, 1976 in Jerusalem.
Returning to Lithuania to complete his studies, Unterman was ordained as a rabbi by Rabbi Refael Shapiro, and by Rabbi Simcha Zelig Reguer, the Dayan of Brisk. He founded  his own yeshiva in the town of Vishnyeva around 1910. Unterman served a variety of roles in the Lithuanian Jewish community until 1924, when he was selected to become the head rabbi of Liverpool. Unterman served in Liverpool for 22 years, becoming an important figure in the English Zionist movement and working to relieve the suffering of refugees in England during the Second World War.
In 1946, Unterman became the Chief Rabbi of Tel Aviv, a position he held for twenty years before being appointed Chief Rabbi of Israel. As Chief Rabbi, Unterman worked to reform the rabbinic court system and reach out to secular Israelis. He also wrote opinions on a variety of religious issues relevant to the young Jewish state, such as religious conversion and marriage law.
He founded two advanced Talmudical academies (kollels), one in Tel Aviv and one in Jerusalem, designed to prepare select students for the rabbinate and educational positions, with an emphasis on systematic study of Talmud and practical halakhah.
Rabbi Unterman died on January 26, 1976 in Jerusalem.
Isser Yehuda Unterman