It happened at 6:50 a.m. on Highway 33, west of Shaw Avenue between Mendota and Firebaugh.
Two cotton modules were on the road when one rear-ended the other.
"There are no visible tire marks in the roadway at this time, so I would suspect they didn't see him until the last second," said Officer Wilson, CHP.
The driver of the truck that rear-ended the second vehicle died at the scene.
He is identified only as a 34-year-old from Biola.
The other driver of the other truck, 59-year-old Martha Parra of Mendota was not injured.