A woman was also in the sedan with the trio and was airlifted to a Brisbane hospital in a critical condition, police said.
A four-wheel-drive allegedly collided with the rear of the sedan on a Western Downs road near Dalby about 11am on Monday.
Police said first responders at the Dalby Jandowae Rd crash at Jimbour East were met with "traumatic" scenes.
"You can just imagine what it was like driving into something like this," Acting Inspector Greg Wheeler told reporters.
"It was pretty horrific actually, for everyone involved.
"Whenever there's children involved it's always extra traumatic for everyone involved."
The father and two children died at the scene.
"The two children were occupants in the rear seat and their father in the front has also died as a result," Insp Wheeler said.
Dalby Jandowae Rd west of Brisbane was closed for hours after the fatal crash on Monday morning. (Supplied/AAP PHOTOS)
Multiple emergency services crews arrived before an RACQ LifeFlight Rescue helicopter landed on the road which was closed for hours.
LifeFlight Rescue said the woman in the sedan was in her 40s and had suffered "multiple traumatic" injuries.
They worked with paramedics to stabilise the woman's condition before she was airlifted to Royal Brisbane and Women's Hospital.
The man driving the 4WD has been taken to Dalby hospital with significant but "non-life threatening" injuries.
Queensland Police Commissioner Steve Gollschewski said the crash would be investigated but issued a warning.
"People on the road need to obey the rules of the road and drive to the conditions," he told reporters.
"The entire leadership team has committed to doing more in the road safety space because too many Queenslanders are losing their lives."
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