Graner, the first soldier to be tried on charges arising from the scandal, was convicted of all five charges and faces up to 15 years behind bars.
The jury took less than five hours to reach the verdict.
The verdict came after a five-day trial in which prosecutors depicted Graner as a sadistic soldier who took great pleasure in seeing detainees suffer. He was accused of stacking naked prisoners in a human pyramid and later ordering them to masturbate while other soldiers took photographs. He also allegedly punched one man in the head hard enough to knock him out, and struck an injured prisoner with a collapsible metal stick.
The jury of four Army officers and six senior enlisted men rejected the defense argument that Graner and other guards were merely following orders from intelligence agents at Abu Ghraib when they roughed up the detainees.
The defense -- 'I was just following orders' -- obviously didn't work before this military jury, which did not have to agree unanimously on the verdicts, notes CBS News Legal Analyst Andrew Cohen. And the likelihood of a reversal on appeal is even more remote than it would be in a regular criminal proceeding in civilian court, Cohen notes.
Graner, a 36-year-old reservist from Uniontown, Pa., was convicted of conspiracy, assault, maltreating prisoners, dereliction of duty and committing indecent acts.
Each count required that at least seven of the 10 jurors to agree for conviction.
The panel of four Army officers and six senior enlisted men began their deliberations at late morning.
"It was for sport, for laughs," Graveline told jurors. "What we have here is plain abuse. There is no justification."
Defense lawyer Guy Womack countered that his client and other Abu Ghraib guards were under extreme pressure from intelligence agents to use physical violence to prepare detainees for questioning.
"It was a persistent, consistent set of orders," said Womack. "To soften up the detainees, to do things so we can interrogate them successfully in support of our mission. ... We had men and women being killed."
Testimony this week from fellow soldiers, officers and detainees themselves painted Graner as an intense lone wolf who liked to take charge.
One detainee, Hussein Mutar, said in taped testimony that he was hooded and helpless on a night in 2003 when he fell into the hands of Graner and other American guards at Abu Ghraib prison.
Mutar, arrested in Baghdad for theft, ended up as the top man in a naked human pyramid allegedly built by Graner while female soldiers watched and others took photos.
The detainee also said "the Americans were torturing us like it was theater to them," CBS News Correspondent Bob McNamara reports.
"Even Saddam didn't do that," the detainee said.
Womack reminded jurors that Saddam Hussein was not yet in U.S. custody when the alleged abuse happened.
"There was somebody very important on everybody's mind," he said. "Wouldn't it be logical to have your interrogators use pressure to get information to try to find him?"
Womack described the notorious photos taken inside the prison as "gallows humor" arising from unrelenting stress felt by the Abu Ghraib guards.
He also tried to plant the seed that Graner and the other low-level guards were being used in a cover-up to protect Army officers once those photos went public.
Graner did not testify during the four-day trial, which included testimony from three guards who had made plea deals with prosecutors.
Two other guards are awaiting trial, along with Pfc. Lynndie England, a clerk at Abu Ghraib who last fall gave birth to a baby believed to be fathered by Graner.
Womack said Thursday that there was no need for Graner to tell his version of what went on inside the prison because his other witnesses were so effective in making the case.
Legal Analyst Cohen doesn't fault Graner's defense team.
"I don't know what else Graner's attorneys could have done. I mean, those photos essentially speak for themselves and suggest criminal conduct and the only available defense was the one they used. The deck was stacked against him once charges were filed, especially after his supervisors refused to back him up,'' said Cohen.
The final two witnesses testified that intelligence officers wanted detainees roughed up, and that they praised guards for their performance.
Graveline used some of Graner's own e-mails as evidence of how much he enjoyed the pain he inflicted on detainees. In one e-mail, he described beating on prisoners as "a good upper-body workout, but hard on the hands."
The e-mail messages were given to jurors Tuesday. The New York Times, which said it got them from a person close to the defense, reported that they were sent to Graner's family and friends, including his young children.
The shocking photos of reservists abusing and sexually humiliating prisoners were first broadcast on CBS's "60 Minutes II" in April. The photos showed naked detainees posed in sexual positions, hooked to electrodes and tethered to a leash.
A month later, President Bush urged Defense Secretary Donald Rumsfeld to make sure that any guilty U.S. soldiers are punished for "shameful and appalling acts." Many critics called for Rumsfeld to step down in the aftermath of the scandal.
Graner's demeanor at the beginning of the trial was upbeat, telling reporters at one point, "Whatever happens is going to happen, but I still feel it's going to be on the positive side, and I'm going to have a smile on my face." As the trial wore on, his expressions grew more stoic.
Two other guards from the 372nd Military Police Company, a reserve unit from Cresaptown, Md., are awaiting trial, along with Pfc. Lynndie England, a clerk at Abu Ghraib who last fall gave birth to a baby believed to be fathered by Graner.