Police said they are concerned for the welfare of Clive Gasston from Brighton.
Clive, 56, was last seen in Brighton on Friday afternoon (June 22), police said.
He was described to police as white, 5ft 6in, and with short dark brown hair. It is unknown what Clive was last wearing but he often wears a khaki green coat, shorts and dark coloured trainers, according to police.
Sergeant Vincent Lam said: “Clive enjoys being outdoors and he could be taking shelter in an open space, such as a park.
“He has links across Brighton, Hove and Worthing and would either be travelling by foot or taking public transport.
“We are appealing for the public to keep an eye out for Clive and to get in contact with us immediately if you see him.”
If you have any information on Clive’s whereabouts please report online or call 101 quoting reference 1647 of 22/06.