Weiss received his semikhah (rabbinical ordination) at the Rabbi Isaac Elchanan Theological Seminary of Yeshiva University in 1968.

Weiss, who had finished his training at Yeshiva University a few years earlier and held pulpits in Creve Coeur, Missouri and Monsey, New York, became the synagogue's rabbi in 1973.

"[16] In 1999 Weiss founded Yeshivat Chovevei Torah (YCT), a rabbinic seminary in the Riverdale neighborhood of the Bronx after resigning from Yeshiva University, where he had taught at Stern College for Women for decades.

On November 3, 2015 the Moetzes of Agudath Israel of America declared Open Orthodoxy, YCT, Yeshivat Maharat and other affiliated entities to be similar to other dissident movements throughout Jewish history in having rejected basic tenets of Judaism.

[30] Weiss has been vocal on many issues, including emigration and absorption of Soviet Jews, clemency for Jonathan Pollard, supporting Israel, preserving Holocaust memorials, and exposing antisemitism.

The book focuses on how grassroots activism and acts of civil disobedience led to important policy changes for the Soviet Jews.

[31] Weiss has served as personal rabbi to Jonathan Pollard,[41] an American who spied for Israel sentenced to life in prison in 1987.

[44] In April 2002 Weiss organized a pro-Israel rally on the National Mall in Washington, D.C.,[45] and a boycott of several large newspapers perceived as having an anti-Israeli bias.

[3] In a July 15, 2015, Haaretz opinion piece, Weiss applauded the U.S. Supreme Court decision legalizing same-sex marriage, which he saw as a part of maintaining the separation of church and state and protecting his right to refuse to perform gay weddings.

"If I welcome with open arms those who do not observe Sabbath, Kashrut or family purity laws, I must welcome, even more so, homosexual Jews, as they are born with their orientation.

The group – dressed in concentration camp clothing – scaled the walls of the convent, blew a shofar, and screamed anti-Nazi slogans.

[53] Along with Rosa Sacharin of Glasgow, Scotland, Weiss sued the American Jewish Committee in New York state court in 2003 to stop the construction of a path through the Belzec extermination camp in Poland.