The former Prison Break star was arrested on Sunday (22Apr12), a day after police were called to Playboy Playmate Ashley Mattingly's Beverly Hills apartment amid reports of a bust-up.
He was placed on $50,000 (£31,000) bail and his lawyer, Harland Braun, insisted his client had been wrongly accused.
Garrison told TMZ.com, "He was dog sitting on the third floor and as he was leaving he saw his ex-girlfriend in the lobby, and she became agitated and took his phone and threw it up against the wall. He basically wanted to get out of there, so he took her by the shoulders to sit her down on a chair. He didn't hit her."
But the Los Angeles County District Attorney has since decided to press charges against the actor after studying CCTV video footage of the heated exchange, which is said to have taken place hours after the couple split.
The misdemeanour carries a punishment of up to a year behind bars, but Garrison could find himself in further trouble if he is found to have violated his probation from his 2007 conviction for vehicular manslaughter and drink driving. He was released from prison in 2009 after serving part of a 40-month sentence for the charges.