"I apologize to those I let down - my family, my friends and most of all the people of Niles," Blase told U.S. District Judge Wayne R. Andersen. "I was wrong."
Blase recently resigned as mayor after serving more than 45 years in the office.
He pleaded guilty in a deal with prosecutors to one count of mail fraud involving the kickback scheme that began in 1974 and continued through 2006. He also pleaded guilty to failing to report the money he received as kickbacks on his 2005 federal income tax return.
In return for his guilty plea, prosecutors agreed to drop nine other counts.
Blase said he paid the $421,450 he received into a company he controlled.
Responding to Blase's apology, Andersen seemed sympathetic and said: "The good things that happened fortunately will not be undone."
Andersen tentatively set sentencing for Jan. 29.
The mail fraud count carries a maximum sentence of 20 years in prison and a fine of $250,000 or twice the proceeds of the crime. Filing a false tax return carries a maximum of three years in prison and a $100,000 fine.
At his age, Blase is unlikely to get anything like the maximum on either count for a first offense.
(This version CORRECTS Corrects that he said he put money into a company he controlled, not paying for paralegals hired by the suburb; ADDS that he did mayoral favors for companies that did business with the insurance agency.)