[1] During his tenure, he developed the Lithuanian-style, Haredi but non-Hasidic yeshiva into the largest post-graduate Torah institution in the world.

He later studied in the Kaminetz yeshiva in Poland and became a student of Rabbi Baruch Ber Leibowitz.

[2][4] Kotler supervised the opening of 30 Lakewood-style kollels in 30 cities,[9] including Los Angeles, Detroit, Toronto, Montreal, Boston, Long Beach, New York, Scranton, Pennsylvania, Miami Beach, Denver,[1] Pittsburgh, Deal, New Jersey, and Melbourne.

[1] Kotler and Wachtfogel oversaw the opening of community kollels in cities including Passaic, New Jersey (a kollel which developed into the Yeshiva Gedola of Passaic),[11] Chicago, Pittsburgh, Detroit, Los Angeles, Toronto,[1] and Melbourne]], Australia.

[12] Kotler served on the Moetzes Gedolei HaTorah of Agudath Israel of America and the rabbinical boards of the Torah Umesorah National Society for Hebrew Day Schools and Chinuch Atzmai.

Kotler served as rosh yeshiva for nineteen years, seven months, and one day, exactly the same amount of time as did his father.

[4] This extraordinary coincidence was noted throughout the Torah world and seen as a sign that he had been a worthy son and successor who carried on his father's mission.