The 43-year-old faced four misdemeanor counts of not filing federal income tax returns from 2006 to 2009. Over that time, he allegedly made more than $1 million, including income from a charity he founded.
The judge asked Zorich if he knew he was wrong not to file the returns.
"Yes, your honor," Zorich said, wearing a black suit and tie.
His attorney previously said Zorich was looking forward to putting the case behind him.
The Chicago native was on the 1988 Notre Dame team that won a national championship. He played for the Bears from 1991 to 1996 and ended his career with the Washington Redskins in 1997.
Zorich must pay $71,000 in back taxes as part of a plea agreement. He is to be sentenced July 12.
Each count carries a maximum sentence of a year in prison and a $100,000 fine.