In a 6-3 split decision, the court refused to grant Ryan or co-defendant Larry Warner the so-called "en banc" hearing.
Ryan, a Republican who gained national prominence as governor for his opposition to the death penalty, was sentenced to 6 1/2 years in federal prison after his conviction. But the sentence had been put on hold and he remained free while the request for another hearing was pending.
It was not clear from Thursday's ruling whether Ryan would now be required to report to prison. Ryan did not return a message left on his cell phone, and the office of his attorney James R. Thompson said it had had no immediate comment. Thompson, himself a former governor, had said earlier that the case would be fought to the U.S. Supreme Court if necessary.
Ryan was convicted of taking payoffs from political insiders in exchange for state business while he was secretary of state from 1991 to 1999 and governor from 1999 to 2003.
In 2000, Ryan declared a moratorium on executions after 13 Illinois death row inmates were found to have been wrongly convicted. Then, days before he left office, he emptied out the state's death row, commuting the sentences of all 167 inmates to life in prison.
But the federal investigation of the secretary of state's office under Ryan eventually ensnared him. It had been speeded up after six children died in 1994 in a fiery accident involving a truck driver who got his license illegally.
Authorities eventually found that unqualified truck drivers had obtained licenses through bribes. Federal prosecutors began convicting his employees and friends, moving closer and closer to Ryan.
Thursday's order from the six majority judges was just one paragraph long and gave no explanation for their refusal to hold a hearing.
Ryan's request for a new trial cited problems that had surfaced during the jury's lengthy deliberations, including the dismissal of a juror who had allegedly snored and another who failed to disclose her arrest record. His lawyers argued that the questioning of jury panel members about the problems had intimidated them and affected their impartiality. Prosecutors scoffed at the notion.