There are
1,585 mi
from Harlingen, TX to Fullerton, CA
That's the driving distance. It would take 1 day 3 hours to go from Harlingen, Texas to Fullerton, California.
The flight distance (direct flight from Harlingen, TX to Fullerton, CA) is 1,318.16 mi.
1,585 mi = 2,550.29 kms