The cat was found after a Parcelforce worker drove a company vehicle from the Haydock area of Merseyside, outside St Helens, to Bristol.
The cat is said to have been discovered hiding in the engine area during routine vehicle checks at the end of the 170-mile journey.
The cat, believed to be between 12 and 14 weeks old, was then coaxed out and taken to Zetland Veterinary in Bristol on Thursday (28/7).
There the cat was assessed and checked for a microchip but, unfortunately, vets say they were not able to find one due to his age.
This makes the possibility of a reunion more difficult, vets said, but are doing all they can to find his owner.
Zetland posted a picture of the cat on Facebook and said: “This young lad jumped under a van bonnet and has travelled from Haydock, near Liverpool.
“Luckily he has no visible injuries but we are now on the hunt for his owners.”
Vikki Flynn, a student veterinary nurse at the Redland practice, told Bristol Live: “He’s quite underweight and he was a bit dehydrated when he came in.
“We found ear mites in his ears and they were really dirty and he is showing signs of cat flu.
“He’s not in tip top condition but considering he’s been under a van bonnet he’s been quite lucky.
“We need to give it a bit more time to potentially reach the owner. It will probably be about seven days and then we will look to rehome him.
“We do reunite cats quite often with their owners who have been missing for months and years, which is why it’s so important to microchip your cat.”
Anyone who recognises the cat should call the practice on 0117 9445111