The officer noticed Locklear's car parked on a state highway and blocking a lane in Montecito, a wealthy community about 90 miles northwest of Los Angeles. She was believed to be alone in the car, Marshall said.
"In talking with her, (the officer) determines that she seems to be under the influence of something," Marshall said.
Locklear was taken to the police station, where she was tested for alcohol and drugs. She was booked at 7 p.m. on suspicion of driving under the influence of prescription medication. She was later released from custody.
Calls to Locklear's publicists were not immediately returned. Locklear's TV credits include "T.J. Hooker," "Dynasty," "Melrose Place" and "Spin City," and her film roles include "The Perfect Man" and "Uptown Girls."
Locklear checked into a medical clinic in June to seek treatment for anxiety and depression.
Last year, she got a divorce from Bon Jovi guitarist Richie Sambora after 11 years of marriage. They have a daughter, Ava Elizabeth.