The former governor could face up to five years in prison on the one conviction, lying to federal agents. U.S. Attorney Patrick Fitzgerald said his office planned to retry the case soon.
"For all practical purposes, we are in the mode of being close to jury selection for a retrial," Fitzgerald said.
Outside the courthouse, Blagojevich insisted, "I didn't break any laws."
"Let me also say this to the people of Illinois -- that from the very beginning this all happened, I told them I did not let them down," he said.
Blagojevich, 53, said he would appeal the single conviction on what he called a "nebulous" charge.
"I didn't break any laws,"he said. "I did not lie to the FBI."
The verdict by the jury of six men and six women capped a long and very public career demise of the politician with the trademark helmet hairdo, who climbed the ladder of public life -- going from Cook County prosecutor to state representative to congressman to governor -- only to take a Nixonian-like fall by being impeached by the Senate by a resounding of 59-0 vote on Jan. 29, 2009.
The verdict, which followed seven weeks of testimony and two of deliberations, fell far short of what prosecutors had hoped for when they announced the indictment. In a December 2008 news conference, Fitzgerald alleged Blagojevich was involved in a "corruption crime spree." The federal prosecutor added, with a touch of the melodramatic, that the Democratic governor's crimes "would make Lincoln turn over in his grave."
Blagojevich said after the verdict that Fitzgerald threw everything "but the kitchen sink" at him -- and still couldn't prove his case.
"The federal government, this particular prosecutor did everything he could to target and prosecute and persecute me," he said.
Blagojevich's brother Robert was also charged in the case, but the jury deadlocked on all four counts against him.
Judge James B. Zagel scheduled an Aug. 26 hearing on the government's plans to retry the former governor.
Some ex-federal prosecutors told AOL News that the conviction, even if it was only on one felony count, couldn't be taken lightly. But William Sullivan, a former federal prosecutor for the District of Columbia, said prosecutors couldn't be happy with the outcome.
"Certainly the jurors' inability to reach a unanimous verdict on so many counts has to be viewed as disappointing result for prosecutors," said Sullivan, now a defense attorney with Winston & Strawn.
The highly publicized case not only exposed an ugly side of the Blagojevich governorship, but embarrassed some people in high places -- including Rep. Jesse Jackson Jr., D-Ill., and Obama himself, whose names surfaced during testimony . It also provided more fodder to cynics who believe Chicago politics are incurably corrupt.
Blagojevich faced a daunting 24 counts. On Thursday, after 12 days of deliberation, jurors informed Zagel that they had come to agreement on two counts and were deadlocked on 11 others. On top of that, they hadn't even gotten to the other 11 counts.
But things seemed to pick up this week. On Monday, jurors asked for a transcript of a witness's testimony, and by today, the judge told the Blagojevich brothers and their attorneys to stay near the courthouse, hinting that a verdict was near.
The 113-page indictment was chock full of allegations. The sexiest alleged that Blagojevich tried to sell the Senate seat Obama vacated when he won the presidency.
A juror told The Associated Press that the panel was deadlocked 11-1 in favor of convicting Blagojevich on that charge. A female holdout "just didn't see what we all saw," said Erik Sarnello, 21.
The ex-governor was also accused of trying to extort money from then-Rep. Rahm Emanuel, now Obama's chief of staff, and the CEO of the children's hospital.
Patrick Magoon, CEO of Children's Memorial Hospital, testified during the trial that days after Blagojevich promised $10 million in state funds for the hospital, brother Robert called asking for $25,000 in campaign donations.
"I felt threatened. I felt at risk, and I felt a little angry," Magoon testified.
Prosecutors introduced embarrassing evidence alleging that Jackson attended a meeting in 2008 in which fundraiser Raghuveer Nayak discussed raising $1 million for Blagojevich in exchange for the governor appointing Jackson to Obama's Senate seat.
Prosecutors portrayed Blagojevich as someone with money problems who tried shaking down people for financial gain. While the ex-governor did not testify in trial, his brother Robert did. Robert denied ever working with his brother to sell the Obama seat.
Prosecutors also played an FBI recording about the Senate seat in which Blagojevich said: "I"ve got this thing and it's f---ing golden and I'm not giving it up for f---ing nothing."