Kim Seber, aged 67, was last seen at around 8.30pm last night (13/1) in Pemberton Road, Slough.
Kim is a white man, around 5ft 4ins tall and of medium build with grey hair and blue eyes.
He was last seen wearing dark blue tracksuit bottoms, blue trainers and a black North Face fleece and a black gilet.
He is known to frequent the Boulter Lock area of Maidenhead, Taplow and the Britwell area of Slough.
Investigating officer Sergeant Will Gilbert, based at Slough police station, said: “We are making an urgent appeal to the public in our search for Kim, who went missing on Thursday evening.
“This disappearance is out of character for Kim, and we are growing increasingly concerned for his welfare, particularly given the cold weather.
“I would ask the public to call us immediately on 999 if you see him, quoting reference number 43220018464.
“Alternatively, if you know of his whereabouts but don’t have him in sight, please call us on 101.”