John, aged 85, is believed to have left his home address in the Bentinck Street area of north Belfast at around 2am yesterday (Saturday, October 21).
He is around 5ft 8in tall with short grey hair. He has a distinctive scar on his face and wears glasses.
John was last seen wearing a black bomber jacket, dark trousers and a checked flat cap. He may have been wearing slippers, rather than shoes.
John has been pictured walking past the Cityside complex at Yorkgate, in the direction of the city centre, at around 9.15am on Saturday. At approximately 9.50am, he was seen crossing Frederick Street towards Donegall Street.
Sergeant Porter said: “John’s family are very worried as it is completely out of character for him not to contact them.
“If you know of John’s whereabouts, or have any information which may help us find him, please contact police as soon as possible on 101, quoting reference number 1450 of 21/10/23.”