Simpson, who went from American sports idol to celebrity-in-exile after his murder acquittal, could spend the rest of his life in prison.
His attorney said he would appeal.
Many people considered the four-week trial justice delayed. Simpson was cleared in 1995 of murdering his ex-wife, Nicole Brown Simpson, and her friend, Ronald Goldman, in one of the most sensational trials of the 20th century, but was later found liable for the deaths in a civil case.
"I don't like to use the word payback," defense attorney Yale Galanter said. "I can tell you from the beginning my biggest concern ... was whether or not the jury would be able to separate their very strong feelings about Mr. Simpson and judge him fairly and honestly."
The Hall of Fame football star was convicted of kidnapping, armed robbery and 10 other charges for gathering up five men a year ago and storming into a room at a hotel-casino, where the group seized several game balls, plaques and photos. Prosecutors said two of the men with him were armed; one of them said Simpson asked him to bring a gun.
Simpson's co-defendant, Clarence "C.J." Stewart, 54, also was found guilty on all charges and taken into custody.
Simpson showed little emotion as officers handcuffed him and walked him out of the courtroom. His sister, Carmelita Durio, sobbed behind him in the arms of Simpson's friend, Tom Scotto, who said "I love you" as Simpson passed by. As spectators left the courtroom, Durio collapsed.
Jurors made no eye contact with the defendants as they entered the courtroom. They declined to answer questions after the verdict was read.
Galanter said his client had expected the outcome, and in a courthouse conversation with an Associated Press reporter on Thursday, Simpson had implied as much.
Simpson said he was "afraid that I won't get to go to my kids' college graduations after I managed to get them through college."
Galanter said it was not a happy day for anybody. "His only hope is the appellate process," he said.
Clark County spokesman Dan Kulin said prosecutors would not comment until the case was "completely resolved."
Judge Jackie Glass made no comment other than to thank the jury for its service and to deny motions for the defendants to be released on bail.
She refused to give the lawyers extended time to file a motion for new trial, which under Nevada law must be filed within seven days. The attorneys said they needed time to submit a voluminous record.
"I've sat through the trial," Glass said. "If you want a motion for new trial, send me something."
Stewart's attorney, Brent Bryson, also promised to appeal.
"If there was ever a case that should have been severed in the history of jurisprudence, it's this case," he said of unsuccessful attempts to separate Stewart's case from Simpson's because of the "spillover" effect.
From the beginning, Simpson and his lawyers argued the incident was not a robbery, but an attempt to reclaim mementos that had been stolen from him. He said he did not ask anyone to bring a weapon and did not see any guns.
The defense portrayed Simpson as a victim of shady characters who wanted to make a buck off his famous name, and police officers who saw his arrest as an opportunity to "get" him and avenge his acquittal.
Prosecutors said Simpson's ownership of the memorabilia was irrelevant; it was still a crime to try to take things by force.
