The Pasadena Police Department said the officer was conducting a traffic stop in the 300 block of State Highway 225 when the marked patrol unit was struck from behind by another vehicle.
Investigators said the crash caused a chain reaction involving additional vehicles. Four vehicles in total, including the officer's car, were involved in the crash, officials said.
All the vehicles involved were deemed inoperable and were towed from the scene, police said, adding that the officer's patrol unit had significant damage to the front and the rear.
Officials said the officer and two additional drivers involved in the crash were taken to nearby hospitals for medical evaluation. One driver declined medical transportation from the scene, authorities said.
Pasadena PD said its Crash Reconstruction Team responded to the scene and is currently investigating the crash.