The California Highway Patrol tells KERO-TV that the child - whose name has not been released - died Wednesday.
RELATED: Massive pileup crash shuts down I-5 at Grapevine, several injured
Several people were injured in a series of crashes involving up to 50 cars amid thick fog on March 23 near Gorman.
The CHP said Saturday that the child was properly strapped into a car seat at the time of the crash.
The pileup happened along the Grapevine section of I-5, which carries traffic over mountains between greater Los Angeles and the San Joaquin Valley.