It happened just before 9 a.m. in the town of Hilmar on River Road near Kelley Road in Merced County.
The CHP says all three victims are females, but their names and ages have not yet been released.
The only survivor is being treated for burns, and her condition is not known at this point.
Authorities say it's remarkable she survived this terrible accident.
One look at the decimated Dodge truck shows the violent nature of the crash that killed the driver and her front seat passenger.
"The driver for unknown reasons lost control of the vehicle, and the driver side ended up broad-siding this oak tree," Sgt. Jeremy Key of the CHP said.
Authorities say the mangled metal made it difficult to reach the victims, and the truck was on fire when they arrived.
"The vehicle wasn't fully engulfed, however there was some fire that spread into the cab area," Key said.
Despite those challenges, crews rescued the rear passenger. She was flown to a Modesto hospital with second degree burns. Investigators are now trying to figure out what caused the crash.
"The roadway was wet when we initially were on scene, however it's not believed that was a cause of the collision," Key said.
The CHP had to close river road for a short time after the accident while a tow truck removed the wreckage. Officers say they have had other fatal crashes in this area, partly because the lack of a shoulder leaves little room for error.