Golden Dawn deputy Giorgos Germenis was attacked by a group of about 30 people outside a cafeteria in the northern Athens suburb of Maroussi on Saturday.
An off-duty policeman who was with the MP of the neonazi party was also beaten, though a woman who was accompanying them was unharmed.
The attack is said to have occurred around lunchtime, when Germenis was set upon outside the cafeteria by the group.
He was punched and kicked, and also assaulted with pepper spray.
The MP had his injuries seen to at a hospital and was released a few hours later.