Emergency officials responded to the scene near FM 249 and Highway 99 just after 5 p.m. The firefighters were on the way to an apartment fire call when the accident happened.
The impact caused the truck to overturn after it went into a muddy field beside the feeder road. According to the department, the firetruck was traveling south on the feeder road. The pickup truck was going east on 249.
The firetruck had its sirens and emergency lights on, officials said.
Two people inside a pickup truck were also injured.
Officials said the four firefighters and two occupants in the truck were taken to a nearby hospital.
By late Saturday, everyone had been released.
The value of the truck was placed at more than $1 million, but for the fire chief, his thoughts were with those who were involved in the crash.
"I lost a good friend of mine who was with the Houston Fire Department. Thankfully, this turned out better," said Chief Randy Parr.