John Albert Elway, 25, entered his plea Tuesday and was sentenced to one year of probation that includes domestic violence counselling. Prosecutors withdrew an assault charge.
The sentence is a deferred judgment, which means the entire case will be dismissed if Elway completes the counselling and does not reoffend.
Elway was arrested in May after his girlfriend told Denver police that he pulled her from a car by her hair after an argument. She said he shoved her to the ground when she tried to get back inside, causing scrapes to her knees.
Police say Elway then fled and was arrested at his father's home in suburban Denver.
Under the plea, Elway is forbidden from possessing firearms and from having contact with the woman in the case, court records show.
His attorney, Harvey Steinberg, declined to comment. The plea came ahead of a jury trial that had been scheduled for Monday.
Jack Elway was a standout quarterback at Cherry Creek High School in Englewood before choosing to play at Arizona State. As a redshirt freshman quarterback in spring 2009, he elected to leave the Sun Devils football program.
His father led the Broncos to two Super Bowl titles in his Hall of Fame career.
The Broncos have described the younger Elway's court case as a family matter and declined to comment.