The incident took place between 8pm and 8.30pm Tuesday, October 17, on Bathurst Road.
A silver Ford Focus pulled up and a man jumped out of the passenger’s side door and assaulted a teenage girl and boy who were walking with a group of friends.
Police are appealing for information and witnesses following an assault in Hemel Hempstead.
The man then got back into the car, which drove off.
The girl received a minor facial injury, the boy was not injured during the incident.
PC Dean Childs-O’Leary, who is investigating, said: “I am appealing to anyone who witnessed the incident on Bathurst Road or has information that could help with our enquiries.”