BEVERLY HILLS, Calif. — One of the country’s most renowned sushi restaurants, Urasawa, sits in a small alcove above Rodeo Drive here. A typical bill for two people easily tops $1,000. Over an evening that can stretch to three hours, diners are served dishes dotted with caviar and 24-karat gold flakes (for the iron, the chef notes).

But workers in the back kitchen are routinely denied overtime pay and forbidden from taking breaks, according to former employees and a California Labor Department investigation. Now, the chef and owner, Hiroyuki Urasawa, is battling state and civil claims that he withheld tens of thousands of dollars in wages and overtime from workers. One former employee who left the restaurant last year said he resorted to urinating in the sink meant for cleaning mops after being told the men’s restroom was for customers only during business hours.

Each night, Mr. Urasawa stands behind a pristine sushi bar serving more than a dozen dishes, each with an elaborate description of the provenance of the ingredients, mostly imported from Japan. With an affable smile, he happily accepts sake from diners, who can spend hundreds of dollars on a bottle.

“It was always about the customers, making sure that they were happy,” said Heriberto Zamora, 26, who worked at the restaurant for more than five years and has filed a civil suit for back pay. “None of the employees were treated very well. We knew people were paying a lot to eat there, but for us it was no different.”