Detectives say the deputy was responding to reports of a driver headed westbound in the eastbound lanes of SR-522 around 1 a.m.
"As the sergeant crested the hill, he observed the vehicle coming directly at him," Washington State Patrol Sergeant Matthew Sloan said.
The deputy swerved to miss the vehicle, struck a concrete barrier, and rolled his patrol car.
The wrong-way driver kept going in what troopers say was either a silver or maroon truck.
The patrol car was totaled, and the deputy was taken to a nearby hospital with minor injuries to his hand.