Authorities say 42-year-old Derek Martin and his 44-year-old brother James Martin were driving on Beal Packing Road, a two-lane dirt road which runs off Highway 177, about eight miles west of Bonifay.
They say Derick, who was driving, apparently lost control of the truck as they were crossing a one-lane wooden bridge.
The truck went off the bridge and into a stream below. It landed on its side in the water with most of the vehicle submerged.
Derick Martin died on the scene. Holmes County paramedics took James Martin to Doctor's Memorial Hospital in Bonifay. He's expected to recover.
Apparently neither man was wearing a seat belt.