Police Scotland are investigating the attack on the man as he carried out his deliveries last Friday October 9.
The postman was delivering in Syme Road at around 10.30 am when he was assaulted by a man while in a block of flats.
The only description of the man is that he was wearing a light blue coloured hooded top with the hood up. The man then ran off after the assault.
Constable Lyndsey Nicholson of Police Scotland at Dumfries said: “This appears to be a completely unprovoked attack on a postman going about his deliveries.
“As a result of this assault the postman received bruising to his face and a black eye.
“Anyone who was in the Syme Road area around this time is asked to call us at Dumfries on 101 if they can help identify this man.”