The crash occurred at about 7:15 a.m. on Archibald Avenue, just north of the 60 Freeway in Ontario.
Both the officer and the truck were traveling northbound. Ontario police say the officer was on-duty but not responding to a call at the time of the incident. The semi was trying to turn into an IHOP when the crash occurred.
The officer ended up in the driveway of the restaurant and was airlifted to the hospital with severe injuries. His exact condition was not immediately released. The driver of the semi, identified as a 43-year-old man from Newhall, was not injured.
Archibald Avenue was closed in both directions between the 60 Freeway and Philadelphia Street as police investigated the scene.
In a statement released late Tuesday morning, the Ontario Police Department said the injured officer is a 17-year veteran of the force and holds the rank of corporal.
If you have any information about this crash, you're urged to contact the Ontario Police Department at (909) 986-6711.