The plea follows an agreement made last month in which Rizzo admitted forming a money-losing corporation to lessen his tax burden.
Rizzo had already pleaded no contest to 69 state corruption charges related to his actions as Bell city administrator.
Rizzo maintained his silence outside the courthouse, but, inside, he responded to dozens of questions from Federal District Court Judge George King.
Among the questions were: Do you fully understand the charges? Did you become a party to a conspiracy? Did you sign an income tax return that was false?
"Yes, your honor," Rizzo repeated throughout the half-hour proceeding.
Prosecutors allege that over the course of four years, Rizzo made about $570,000 in illegal deductions.
"As part of this conspiracy, we believe that the tax loss to the IRS is about $300,000," said U.S. Attorney's Office spokesman Thom Mrozek.
Rizzo's attorney, James Spertus, says the deal spares taxpayers the expense of a big trial.
"I would think that the community and the public should want to treat people who accept responsibility differently than those who do not, Spertus said, referring to Angela Spaccia, Rizzo's assistant city manager.
Spaccia had denied culpability, went to trial and was convicted on 11 counts. She faces a potential term of 10 to 12 years. Rizzo believes he should get less.
"I think that hopefully at the end of these pathways, Mr. Rizzo will be recognized as someone who tried to make things right as opposed to fighting every step of the way," said Spertus.
The tax charges suggest that Spaccia may later face federal charges as well. Documents say Rizzo and a person with the initials A.S. claimed bogus losses. However, Spaccia is not specifically named.
Rizzo now looks ahead to how much time he will serve and where he will serve it. His attorney is pursuing a sentencing date on the federal charges that will precede his sentencing on the 69 state charges.
That sequence could help his chances of going to a federal facility instead of a state prison. As for the penalty, the tax evasion charges alone could send him there for as many as eight years.