Robbers hit a man over the head and stole his Rolex near East Dulwich station last Monday.
Police believe the 34-year-old victim was followed from a shop before being attacked on Melbourne Grove at around 6pm on November 2.
Officers say he was hit over the head before two suspects stole his Rolex watch, a laptop and iPad.
Investigating officers have not released a description of the attackers but are urging any potential witnesses to get in touch.
It is the latest in a spate of violent robberies in the East Dulwich area, though there is no suggestion any are linked.
A 19-year-old was stabbed and robbed in Gowlett Road on November 3, and a man was tied up and threatened with a gun in a home burglary in Whateley Road in September.
Anyone with information should call police on 101.