Weiss is the author of the novel Cock-a-Doodle-Doo (1996) and the non-fiction book American Taboo: A Murder In The Peace Corps (2004). He co-edited The Goldstone Report: The Legacy of the Landmark Investigation of the Gaza Conflict (2011) with Adam Horowitz and Lizzy Ratner.
In 2006 he began writing a daily blog called Mondoweiss for The New York Observer website which began to focus only on "Jewish issues" like "the Iraq disaster and my Jewishness, Zionism, neo-conservatism, Israel, Palestine." In the spring of 2007, he began Mondoweiss as an independent blog.
Weiss praised an article by Ron Unz alleging that Jews are overrepresented at Ivy League universities. According to the Anti-Defamation League, Weiss is significantly funded by Unz's Unz Foundation. For example, in 2009, 2010, and 2011, Weiss received payments of $60,000 from Unz.
Allegations of antisemitism
Weiss and his website have been accused of antisemitism. According to Elliot Kaufman, writing in The Stanford Review, Mondoweiss "often publishes astonishingly anti-Semitic material, using classic anti-Semitic imagery such as depicting Jews as spiders, cockroaches, or octopuses with tentacles controlling others, and Holocaust inversion. Its hatred of Israel is as deep as it is vicious."
In 2015, David Bernstein, writing for The Washington Post, called the website a "hate site", and listed quotes from Weiss that he asserted were anti-Semitic. This included Weiss's claim that "the Israel lobby ... reflected a contract the American establishment had made with Jews to drive the economy in the 1970s", which Bernstein likened to a belief in an "Elders of Zion type group".