The collision happened just after 2 a.m. at the intersection of 5th Avenue and James Street.
Police say the woman made a left turn in front of the oncoming officer as the light changed from green to yellow and their vehicles collided head-on.
The woman was taken to Harborview Medical Center to be checked for a leg injury. The officer was treated at the scene for knee pain.
Both vehicles sustained significant damage.
Police say it doesn't appear the woman was impaired.