Prof Lipstadt wrote that she ignored the protesters, who were from the group Law Students for Justice in Palestine and stood beside her holding signs attacking Israel.
The historian said she “had far more important things to discuss”.
“In the talk, when I spoke about antisemitism from the left, I mentioned that many people refuse to see it as legitimate,” she said.
“They dismiss claims of antisemitism as simply being a sop to protect Israel. This is the only prejudice those on the left refuse to take seriously”.
One protester held a sign in support of the anti-Israel Boycott, Divestment and Sanctions (BDS) movement, while another held a sign declaring anti-Zionism was not antisemitism.
Prof Lipstadt was sued for libel in 1996 by British historian David Irving after she referred to him as a Holocaust denier in her book Denying the Holocaust.
She won the case in 2000, after a trial which was dramatised in the 2016 film Denial.
Prof Lipstadt is known as fiercely defensive of free-speech and has argued against both outlawing Holocaust denial and "safe spaces" at universities.
