The collision happened just before 12:45 a.m. on Beach Boulevard near the 22 Freeway.
Officers responded to the scene and found a person dead and another unresponsive.
There were no passengers in either car, which were both significantly destroyed in the crash.
The second victim was transported to a nearby hospital, where the person later died.
Police are still investigating what caused the crash. They're asking any witnesses to call the Garden Grove Police Department.