Firefighters from Castleford Station were called to free the worker from his post van on Newton Lane, Ledston at around 8pm on Wednesday, April 4.
Watch Commander David Smith said the van had been driven past a road closed due to flooding sign and had become stranded in around 3ft of flood water.
Two firefighters in flood suits led him away to safety.
The parcel van was recovered the following day after the water subsided, Watch Commander Smith said.
He said: "This incident highlights the dangers of ignoring signs and driving through flood water, which can potentially put lives at risk."