The Only Way Is Essex star was thrown to the ground by two men who he had agreed to take a photo with in Hammersmith.
The men proceeded to rip off and steal his £10,000 Rolex watch, reports The Sun.
Essex said: "I got a knock on my car window asking if I was Joey Essex and if I would have my picture taken.
"We did the picture and when I put some money in the parking ticket machine, the geezers got hold of me and threw me over.
"It wasn't until I got up that I realised they had nicked my watch and when I hit one of them back, he got out a knife."
A police spokesman said: "Officers from the Robbery Squad at Hammersmith and Fulham are investigating the incident."
Last year, The Only Way Is Essex stars Sam and Billie Faiers were attacked by a female gang.
Joey Essex and Sam Faiers recently said that they were interested in starring in a spin-off series.