The Risky Business star was stopped Oct. 30 for a traffic violation, police say. According to a statement, "Officers immediately detected the odor of alcohol."
The actress subsequently failed a field sobriety test, and she later blew a .09 on a Breathalyzer (.08 is the legal limit).
"She was very cooperative during the arrest," said Beverly Hills police spokesman Tony Lee.
DeMornay, 48, was booked around midnight and posted $5,000 bail. Her court date is pending.