The crash was reported at 8:26 p.m., said California Highway Patrol Officer Patrick Kimball.
A witness reported that the vehicle fell off the freeway and landed at the intersection of Michillinda Avenue and East Colorado Boulevard, Kimball said.
Two people died at the scene, he said. The third died at Huntington Memorial Hospital. Their names were withheld pending notification of their next of kin.
Pasadena police Lt. Lemos told reporters there were five people in the vehicle and that three were taken to a trauma center with very serious injuries. One was the person pronounced dead at the hospital. The conditions of the others were not available.