The assaulter got near the open vehicle in which Kejriwal was travelling during the road show and tried to hit him.
The former Delhi chief minister was hit near his neck, but he was not injured.
The attacker was immediately pinned down by Aam Aadmi Party supporters and beaten up. He was taken away by police who were present at the spot.
Charkhi Dadri is about 125 km from New Delhi.