The drama happened near the Preston Island on the A5, in the direction of the M54 and Telford.
Fifteen firefighters raced to the scene from Shrewsbury and Wellington.
No one was injured, but John Griffiths, a Shrewsbury station manager from Shropshire Fire and Rescue Service, said the van was a write-off.
He said the driver noticed smoke coming from the dashboard and pulled over, with the vehicle catching light within five minutes.
Both carriageways were temporarily closed in both directions by firefighters as smoke billowed across them, with firefighters wearing breathing apparatus to tackle the fire.
One lane of the A5 in the eastbound direction was blocked after the fire was brought under control, with Highways Agency officials contacted to help arrange its removal.
The fire happened shortly before 3pm yesterday.
Mr Griffiths said: "It was a commercial van that was travelling eastbound towards Wellington and the driver saw some smoke coming from under the dashboard. Within five minutes the cab was ablaze."
"The fire was concentrated within the driving compartment. The van is a write-off.
"There was smoke affecting both carriageways. Once the fire was under control, one lane was opened up again."
Two fire engines were sent to the scene from Shrewsbury, with one from Wellington.