The 26-year-old actress was arrested around 3 a.m. Friday in West Hollywood.
The Los Angeles County sheriff's department says that Bynes attempted to pass a patrol car making a right turn when she hit it. Deputies who arrested her suspect she was drunk at the time.
Bynes is being held on $5,000 bail. Her publicist, Melissa Raubvogel, did not immediately return a call and an email from The Associated Press.
The actress appeared in the 2010 film "Easy A" and the Nickelodeon series "What I Like About You."
Deputies say there was paint damage to both cars, but no one was injured.