Joel Andrews went missing from the Fernworthy Resevoir area near Chagford during the early hours of Sunday 22nd May.
Police are becoming increasingly concerned for his welfare as his disappearance appears to be out of character and are appealing for assistance from the public to help locate him.
Joel is from Caldicot but is believed to have family and friends in Monmouth and the Forest of Dean.
A Facebook group has been set up to help find the 24-year-old. 'Joel Andrews Missing' have more than 2,000 members and many are travelling to Devon today to help with the search.
Officers in Devon are liaising with Gwent Police as part of their investigation.
Joel is described as a white man, of slim build, approximately 5' 10" in height, with mousy brown hair, blue eyes, and has a scar on his chin.
He was last seen wearing a grey coloured 'animal' hooded top, blue jeans, a dark green waist length jacket, and a camouflage cap.
Anyone who sees Joel or anyone matching his description is asked to contact 08452 777444 quoting police reference 670 240511.