James entered his plea and was sentenced to 10 days in jail and 24 months of probation. He reported to jail on Friday afternoon but was quickly released and instead put on electronic surveillance for the duration of his sentence.
Deputy District Attorney Alex Gardner had said earlier that it was unlikely James would serve jail time because of overcrowding, and because his offense was relatively minor and he was considered low-risk.
James, who set a Pac-10 freshman record with more than 1,500 yards rushing last season, originally faced five misdemeanor charges, including strangulation, harassment and assault. All but one harassment charge were dropped.
In a statement that was included in court documents related to the case, James apologized to the victim, a former girlfriend. She claimed he grabbed her neck and pushed her to the ground during an argument on Feb. 15.
"I hope to put this matter behind me now and learn from it. I have made a mistake and accept the consequences," the statement said. "I look forward to demonstrating to my University, to my team and to the community that I am a better man than recent events suggest."
James rushed for 1,546 yards last season as a freshman, the ninth-highest total in the nation. He had seven consecutive 100-yard games before Ohio State limited him to 70 in Oregon's 26-17 loss in the Rose Bowl.