At a Philadelphia bar owned by the Barstool Sports founder Dave Portnoy, patrons who order bottle service are offered customizable letter boards, which they can ask staff members to arrange with messages of their choice, such as “break up with him” or “go birds!”

But at least one customer, a Temple University student who visited the bar on Saturday night, asked staff members to arrange the letters on his sign into an antisemitic message. The sign, according to Mr. Portnoy, had a four-letter expletive directed at Jewish people.

The incident has drawn nationwide fury, becoming a symbol of the rise in antisemitism.

Antisemitic episodes in the United States reached a record high in the 12-month period from October 2023 to September 2024, according to figures from the Anti-Defamation League, a civil rights organization.

The group identified more than 10,000 antisemitic incidents — triple the number recorded during the same period a year earlier — which were split into categories including verbal or written harassment, vandalism and physical assault. More than 8,000 of those episodes involved cases of verbal or written harassment, according to the figures.

It was not immediately clear how many customers were involved in the episode at Barstool Sansom Street, in Philadelphia’s Center City neighborhood. The bar said in a statement that it involved a customer whose actions were “deplorable,” but Mr. Portnoy said in a video on Instagram that two customers were involved.

The bar also blamed “misguided” employees who ignored the company’s training and “zero-tolerance policy for discrimination and hate,” and added that the employees had been investigated and fired.