The former "Partridge Family" star was initially stopped for driving with his high beams on. When the officer smelt alcohol, he issued a field sobriety test.
The 63-year-old actor failed the test after blowing a .10. He was cuffed and taken to jail.
The court will treat Cassidy's case as a felony, due to his earlier DUI in Florida.
The actor was later released on $2,500 bail.